Optimized reactor configuration for optimal performance of the aromax catalyst for aromatics synthesis

ABSTRACT

A naphtha reforming reactor system comprising a first reactor comprising a first inlet and a first outlet, wherein the first reactor is configured to operate as an adiabatic reactor, and wherein the first reactor comprises a first naphtha reforming catalyst; and a second reactor comprising a second inlet and a second outlet, wherein the second inlet is in fluid communication with the first outlet of the first reactor, wherein the second reactor is configured to operate as an isothermal reactor, and wherein the second reactor comprises a plurality of tubes disposed within a reactor furnace, a heat source configured to heat the interior of the reactor furnace; and a second naphtha reforming catalyst disposed within the plurality of tubes, wherein the first naphtha reforming catalyst and the second naphtha reforming catalyst are the same or different.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

FIELD

This disclosure relates generally to a system and method for operating acatalytic naphtha reforming process. More particularly, the disclosurerelates to operating a reactor under isothermal naphtha reformingconditions in a catalytic naphtha reforming process.

BACKGROUND

Typical catalytic naphtha reforming processes can be carried out using avariety of reactors containing naphtha reforming catalysts. The naphthareforming process encompasses a number of reactions, which are typicallycarried out in the presence of a catalyst, such as dehydrocyclization,hydrodecyclization, isomerization, hydrogenation, dehydrogenation,hydrocracking, cracking, etc. Naphtha reforming reactions are intendedto convert the paraffins, naphthenes, and olefins present in naphtha toaromatics and hydrogen. Generally, adiabatic reactors are preferred fornaphtha reforming processes, although several adiabatic reactorsoperated in series are usually necessary to achieve a desired conversionand selectivity for the naphtha reforming process.

SUMMARY

Disclosed herein is a method comprising introducing a hydrocarbon feedstream to a first reactor operating under adiabatic naphtha reformingconditions, wherein the first reactor comprises a first naphthareforming catalyst and wherein the hydrocarbon feed stream comprises aconvertible hydrocarbon; converting at least a portion of theconvertible hydrocarbon in the hydrocarbon feed stream to an aromatichydrocarbon in the first reactor to form a first reactor effluent;passing the first reactor effluent from the first reactor to a secondreactor operating under isothermal naphtha reforming conditions, whereinthe second reactor comprises a second naphtha reforming catalyst andwherein the first naphtha reforming catalyst and the second naphthareforming catalyst are the same or different; converting at least anadditional portion of the convertible hydrocarbon in the first reactoreffluent to an additional amount of the aromatic hydrocarbon in thesecond reactor to form a second reactor effluent; and recovering thesecond reactor effluent from the second reactor.

Also disclosed herein is a reactor system comprising a first reactorcomprising a first inlet and a first outlet, wherein the first reactoris configured to operate as an adiabatic reactor, and wherein the firstreactor comprises a first naphtha reforming catalyst; and a secondreactor comprising a second inlet and a second outlet, wherein thesecond inlet is in fluid communication with the first outlet of thefirst reactor, wherein the second reactor is configured to operate as anisothermal reactor, wherein the second reactor comprises a secondnaphtha reforming catalyst, and wherein the first naphtha reformingcatalyst and the second naphtha reforming catalyst are the same ordifferent.

Further disclosed herein is a reactor system comprising a plurality ofadiabatic reactors, wherein each adiabatic reactor of the plurality ofadiabatic reactors comprises a first naphtha reforming catalyst; a feedheader fluidly coupled to at least one of the plurality of adiabaticreactors by one or more feed lines; an intermediate product headerfluidly coupled to at least one of the plurality of adiabatic reactorsby one or more product lines; one or more isothermal reactors fluidlycoupled to the intermediate product header by one or more inlet lines,wherein the one or more isothermal reactors comprise a second naphthareforming catalyst and wherein the first naphtha reforming catalyst andthe second naphtha reforming catalyst are the same or different; and aneffluent header fluidly coupled to the one or more isothermal reactorsby one or more effluent lines, wherein a serial flow path is formed fromthe feed header, through one or more of the plurality of adiabaticreactors, through the intermediate product header, through at least oneof the one or more isothermal reactors, and to the effluent header.

Further disclosed herein is a method comprising introducing ahydrocarbon feed stream to a first reactor operating under adiabaticnaphtha reforming conditions, wherein the first reactor comprises afirst naphtha reforming catalyst, and wherein the hydrocarbon feedstream comprises a convertible hydrocarbon; converting at least aportion of the convertible hydrocarbon in the hydrocarbon feed stream toan aromatic hydrocarbon in the first reactor to form a first reactoreffluent; passing the first reactor effluent from the first reactor to asecond reactor operating under isothermal naphtha reforming conditions,wherein the second reactor comprises a second naphtha reformingcatalyst, and wherein the first naphtha reforming catalyst and thesecond naphtha reforming catalyst are the same or different; convertingat least an additional portion of the convertible hydrocarbon in thefirst reactor effluent to an additional amount of the aromatichydrocarbon in the second reactor to form a second reactor effluent; andrecovering the second reactor effluent from the second reactor, whereinan amount of the first naphtha reforming catalyst in the first reactoris less than an amount of the second naphtha reforming catalyst in thesecond reactor.

Further disclosed herein is a naphtha reforming reactor systemcomprising a first reactor comprising a first inlet and a first outlet,wherein the first reactor is configured to operate as an adiabaticreactor, and wherein the first reactor comprises a first naphthareforming catalyst; and a second reactor comprising a second inlet and asecond outlet, wherein the second inlet is in fluid communication withthe first outlet of the first reactor, wherein the second reactor isconfigured to operate as an isothermal reactor, and wherein the secondreactor comprises a plurality of tubes disposed within a reactorfurnace, a heat source configured to heat the interior of the reactorfurnace; and a second naphtha reforming catalyst disposed within theplurality of tubes, wherein the first naphtha reforming catalyst and thesecond naphtha reforming catalyst are the same or different.

Further disclosed herein is a method comprising introducing ahydrocarbon feed stream to a radial flow reactor operating underadiabatic naphtha reforming conditions, wherein the radial flow reactorcomprises a first naphtha reforming catalyst, and wherein thehydrocarbon feed stream comprises a convertible hydrocarbon; convertingat least a portion of the convertible hydrocarbon in the hydrocarbonfeed stream to an aromatic hydrocarbon in the radial flow reactor toform a first reactor effluent; passing the first reactor effluent fromthe radial flow reactor to a second reactor operating under isothermalnaphtha reforming conditions, wherein the second reactor comprises aplurality of tubes disposed within a reactor furnace, and a secondnaphtha reforming catalyst disposed within the plurality of tubes, andwherein the plurality of tubes are arranged in parallel between an inletand an outlet of the reactor furnace; passing the first reactor effluentthrough the plurality of tubes within the second reactor; converting atleast an additional portion of the convertible hydrocarbon in the firstreactor effluent to an addition amount of the aromatic hydrocarbon inthe second reactor to form a second reactor effluent, wherein theplurality of tubes is heated within the reactor furnace during theconverting; and recovering the second reactor effluent from the secondreactor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of an embodiment of a naphtha reforming processof the present disclosure.

FIG. 2 is a flow diagram of another embodiment of a naphtha reformingprocess of the present disclosure.

FIG. 3 is a flow diagram of yet another embodiment of a naphthareforming process of the present disclosure.

FIG. 4 is a flow diagram of still yet another embodiment of a naphthareforming process of the present disclosure.

FIG. 5A is a flow diagram of still yet another embodiment of a naphthareforming process of the present disclosure.

FIG. 5B is a flow diagram of still yet another embodiment of a naphthareforming process of the present disclosure.

FIG. 6A is a diagram of an embodiment of a graded catalyst bed of thepresent disclosure.

FIG. 6B is a diagram of another embodiment of a graded catalyst bed ofthe present disclosure.

FIG. 7A is a diagram of yet another embodiment of a graded catalyst bedof the present disclosure.

FIG. 7B is a diagram of still yet another embodiment of a gradedcatalyst bed of the present disclosure.

FIG. 8A is a diagram of still yet another embodiment of a gradedcatalyst bed of the present disclosure.

FIG. 8B is a diagram of still yet another embodiment of a gradedcatalyst bed of the present disclosure.

FIG. 9A is a flow diagram of still yet another embodiment of a naphthareforming process of the present disclosure.

FIG. 9B is a flow diagram of still yet another embodiment of a naphthareforming process of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Reforming reactors operating under isothermal naphtha reformingconditions could allow for enhanced naphtha reforming selectivity andconversion, while presenting lower rates of catalyst deactivation thanfound in adiabatic reactors. However, the highly endothermic naphthareforming process complicates the maintenance of isothermal conditionsthroughout the reactor (e.g. the temperature profile) under isothermalnaphtha reforming conditions. Process designs for the maintenance of thereactor temperature profile in isothermal reactors operating atcatalytic naphtha reforming conditions often include additional burnersat the feed entrance to the plurality of tubes that comprise theisothermal reactor. This is to compensate for the strong endotherm asthe initial reforming reactions consume the more easily convertedspecies in the hydrocarbon feed stream. However, this high tube wallheat flux at the upstream end of the plurality of tubes that comprisethe isothermal reactor leads to higher capital cost designs throughhigher cost tube metal alloys. Additionally, the high tube wall heatflux will magnify any operational issues associated with process unitupsets. These issues may be addressed with a reactor system with a highnumber of tubes. However, the additional cost and complexity of thissolution is not optimal for a problem that principally effects theupstream end of the plurality of tubes that comprise the isothermalreactor. Isothermal reactors also present concerns of increased pressuredrop across the catalyst bed. Thus, there is an ongoing need forintegrating isothermal reactors in naphtha reforming processes toincrease conversion and selectivity, while maintaining lower reactortube wall temperatures and lower overall pressure drop.

Disclosed herein are systems, apparatuses, and methods related tocarrying out a naphtha reforming process by employing both adiabaticreactors and isothermal reactors. In an embodiment, a plurality ofreactors can be used to carry out the naphtha reforming reactions, wherethe reactors can comprise at least one reactor operating under adiabaticnaphtha reforming conditions in series with at least one reactoroperating under isothermal naphtha reforming conditions. As is generallyunderstood, naphtha reforming, or simply, a reforming “reaction”typically takes place within a naphtha reforming “reactor.” For purposesof the disclosure herein, the term “reforming reaction” can take placein any suitable naphtha reforming reactor disclosed herein, such as forexample a first reactor, a second reactor, an adiabatic reactor, anisothermal reactor, etc. The naphtha reforming described herein is theprocess for the conversion of aliphatic hydrocarbons found in a naphthastream to aromatic hydrocarbons. Naphtha reforming refers not to one,but to several reactions that take place simultaneously. These naphthareforming reactions include removal of hydrogen from cycloalkanes andalkyl-cycloalkanes, removal of hydrogen from and isomerization ofalkyl-cycloalkanes, and removal of hydrogen from and cyclization ofaliphatic hydrocarbons. Outside of these reactions, side reactions canoccur, including dealkylation of alkylbenzenes, isomerization ofaliphatic hydrocarbons, and hydrocracking reactions which produce lightgaseous hydrocarbons such as methane, ethane, propane, and butane.

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can comprise (i) introducing a hydrocarbon feedstream to a first reactor to form a first reactor effluent, where thefirst reactor operates under adiabatic naphtha reforming conditions, andwhere the first reactor comprises a first naphtha reforming catalyst;(ii) passing the first reactor effluent from the first reactor to asecond reactor to form a second reactor effluent, where the secondreactor operates under isothermal naphtha reforming conditions, andwhere the second reactor comprises a second naphtha reforming catalyst;and (iii) recovering the second reactor effluent from the secondreactor.

In an embodiment, the hydrocarbon feed stream comprises a convertiblehydrocarbon. As used herein, a “hydrocarbon feed stream” or “hydrocarbonstream” comprises hydrocarbons, though components other than moleculescomprising hydrogen and carbon may be present in the stream (e.g.,hydrogen gas). For purposes of the disclosure herein, the termshydrocarbon feed stream” and “hydrocarbon stream” can be usedinterchangeably and refer to the hydrocarbon introduced (e.g., fed) to areactor, such as the first reactor. In some embodiments, a “hydrocarbon”may comprise individual molecules that comprise one or more atoms otherthan hydrogen and carbon (e.g., nitrogen, oxygen, etc.).

Various feedstocks may be suitable for use with naphtha reformingprocesses and generally comprise non-aromatic hydrocarbons. The feed(e.g., hydrocarbon feed stream) to the naphtha reforming systemcomprising an aromatization system can be a mixture of hydrocarbonscomprising C₆ to C₈ hydrocarbons containing up to about 10 wt. %, oralternatively up to about 15 wt. % of C₅ and lighter hydrocarbons (C₅⁻); and containing up to about 10 wt. % of C₉ and heavier hydrocarbons(C₉ ⁺). Suitable feedstocks include hydrocarbon feed streams boilingwithin a temperature range of from about 70° F. (21° C.) to about 450°F. (232° C.), or alternatively from about 120° F. (49° C.) to about 400°F. (204.5° C.). In an embodiment, the hydrocarbon feed stream can have asulfur content of less than about 200 parts per billion by weight(ppbw), alternatively less than about 100 ppbw, alternatively less thanabout 50 ppbw, or alternatively from about 10 ppbw to about 100 ppbw.Examples of suitable feedstocks include straight-run naphthas frompetroleum refining or fractions thereof which have been hydrotreated toremove sulfur and other catalyst poisons. Also suitable are syntheticnaphthas or naphtha fractions derived from other sources such as coal,natural gas, bio-derived hydrocarbons or from processes such asFischer-Tropsch processes, fluid catalytic crackers, and hydrocrackers.

A convertible hydrocarbon may comprise hydrocarbons having six or sevencarbon atoms without an internal quaternary carbon or hydrocarbonshaving six carbon atoms without two adjacent internal tertiary carbons,or mixtures thereof. The convertible hydrocarbons may comprisemethylpentanes, methylhexanes, dimethylpentanes or mixtures thereof,and/or the convertible components may comprise at least one of2-methylpentane, 3-methylpentane, 2,4-dimethylpentane,2,3-dimethylpentane, n-hexane, 2-methylhexane, 3-methylhexane,n-heptane, or mixtures thereof. The feed stream may comprise betweenabout 0.1 wt. % and about 100 wt. % highly branched hydrocarbons. Theconvertible hydrocarbons readily convert to aromatic products withoutproduction of light hydrocarbons.

The hydrocarbon feed stream may comprise highly branched hydrocarbonshaving six or seven carbon atoms with an internal quaternary carbon orhydrocarbons having six carbons atoms and two adjacent internal tertiarycarbons or mixtures thereof. The highly branched hydrocarbons maycomprise dimethylbutanes, trimethylbutanes, dimethylpentanes, ormixtures thereof. The highly branched hydrocarbons with six or sevencarbon atoms with an internal quaternary carbon may comprise, forexample, 2,2-dimethylbutane, 2,2-dimethylpentane, 3,3-dimethylpentane,2,2,3-trimethylbutane, or mixtures thereof. The highly branchedhydrocarbons with six carbon atoms and an adjacent internal tertiarycarbon may comprise 2,3-dimethylbutane. The highly branched hydrocarbonsdo not selectively convert to aromatic products and instead tend toconvert to light hydrocarbons.

An “aromatic hydrocarbon” is a compound containing a cyclicallyconjugated double bond system that follows the Hückel (4n+2) rule andcontains (4n+2) pi-electrons, where n is an integer from 1 to 5.Aromatic hydrocarbons include “arenes” (e.g., benzene, toluene, andxylenes) and “heteroarenes” (heteroaromatic compounds formally derivedfrom arenes by replacement of one or more methine (—C═) carbon atoms ofthe cyclically conjugated double bond system with a trivalent ordivalent heteroatoms, in such a way as to maintain the continuouspi-electron system characteristic of an aromatic system and a number ofout-of-plane pi-electrons corresponding to the Hückel rule (4n+2)). Asdisclosed herein, the term “substituted” may be used to describe anaromatic hydrocarbon, arene, or heteroarene, wherein a non-hydrogenmoiety formally replaces a hydrogen atom in the compound, and isintended to be non-limiting, unless specified otherwise.

As used herein, the term “alkane” refers to a saturated hydrocarboncompound. Other identifiers may be utilized to indicate the presence ofparticular groups, if any, in the alkane (e.g., halogenated alkaneindicates the presence of one or more halogen atoms replacing anequivalent number of hydrogen atoms in the alkane). The term “alkylgroup” is used herein in accordance with the definition specified byIUPAC: a univalent group formed by removing a hydrogen atom from analkane. The alkane or alkyl group may be linear or branched unlessotherwise specified.

A “cycloalkane” is a saturated cyclic hydrocarbon, with or without sidechains, for example, cyclobutane, cyclopentane, cyclohexane, methylcyclopentane, and methyl cyclohexane. Other identifiers may be utilizedto indicate the presence of particular groups, if any, in thecycloalkane (e.g., halogenated cycloalkane indicates the presence of oneor more halogen atoms replacing an equivalent number of hydrogen atomsin the cycloalkane).

In some embodiments, the hydrocarbon feed stream can further comprisehydrogen, as the naphtha reforming process generally employs additionalhydrogen introduced to the reforming reactors (although hydrogen isproduced during the reforming process). The hydrogen can be introducedas fresh hydrogen to the hydrocarbon feed streams entering a reformingreactor, or it can be recovered from reactor effluents and recycled backto the reforming reactor(s).

In some embodiments, the hydrocarbon feed stream can further compriseoxygenates and/or nitrogenates. In an aspect, the hydrocarbon feedstream is initially substantially free of oxygenates and nitrogenates.In such aspects, an oxygenate, a nitrogenate, or both can be added toone or more process streams and/or components in the naphtha reformingsystem disclosed herein.

As used herein, the term “oxygenate” refers to water or any chemicalcompound that forms water under naphtha reforming conditions, such asoxygen, oxygen-containing compounds, hydrogen peroxide, alcohols,ketones, esters, ethers, carbon dioxide, aldehydes, carboxylic acids,lactones, ozone, carbon monoxide, or combinations thereof. In anembodiment, water and/or steam is used as the oxygenate. In anotherembodiment, oxygen may be used as the oxygenate, wherein such oxygenconverts to water in situ within one or more naphtha reforming reactorsunder typical naphtha reforming conditions. Furthermore, the oxygenatecan be any alcohol-containing compound. Nonlimiting examples ofalcohol-containing compounds suitable for use in the present disclosureinclude methanol, ethanol, propanol, isopropanol, butanol, t-butanol,pentanol, amyl alcohol, hexanol, cyclohexanol, phenol, or combinationsthereof. As will be appreciated by one of skill in the art, and with thehelp of this disclosure, the presence of an oxygenate causes a specificamount of water to be present in one or more naphtha reforming reactorsduring the naphtha reforming process. The presence of a specific amountof water in a naphtha reforming reactor can activate or enhanceperformance of the naphtha reforming catalyst.

In an embodiment, the water (e.g., added water and/or produced water)can be introduced to a naphtha reforming reactor in an amount of lessthan about 1,000 ppm, alternatively less than about 100 ppm,alternatively less than about 50 ppm, alternatively from about 0.1 ppmto about 50 ppm, alternatively from about 0.5 ppm to about 25 ppm,alternatively from about 1 ppm to about 20 ppm, alternatively from about2 ppm to about 15 ppm, or alternatively from about 3 ppm to about 10 ppmwater, based on the volume of the hydrocarbon feed stream.

As used herein, the term “nitrogenate” refers to ammonia or any chemicalcompound that forms ammonia under naphtha reforming conditions such asnitrogen, nitrogen-containing compounds, alkyl amines, aromatic amines,pyridines, pyridazines, pyrimidines, pyrazines, triazines, heterocyclicN-oxides, pyrroles, pyrazoles, imadazoles, triazoles, nitriles, amides,ureas, imides, nitro compounds, nitroso compounds, or combinationsthereof. Without wishing to be limited by theory, it is believed thatthe ammonia will improve catalyst activity in much the same way as thewater.

In an embodiment, the ammonia (e.g., added ammonia and/or producedammonia) can be introduced to a naphtha reforming reactor in an amountof less than about 1,000 ppm, alternatively less than about 100 ppm,alternatively less than about 50 ppm, alternatively from about 0.1 ppmto about 50 ppm, alternatively from about 0.5 ppm to about 25 ppm,alternatively from about 1 ppm to about 20 ppm, alternatively from about2 ppm to about 15 ppm, or alternatively from about 3 ppm to about 10 ppmammonia, based on the volume of the hydrocarbon feed stream.

As will be appreciated by one of skill in the art, and with the help ofthis disclosure, any of the oxygenates, nitrogenates, or mixturesthereof disclosed herein can be used alone, in combination, or furthercombined to produce other suitable oxygenates or nitrogenates. In someembodiments, the oxygenate and nitrogenate may be contained within thesame bifunctional compound. The use of oxygenates and/or nitrogenatesfor enhancing the performance of reforming catalysts is described inmore detail in U.S. Pat. Nos. 7,932,425; 8,569,555; and 8,362,310; eachof which is incorporated by reference herein in its entirety.

Various upstream hydrocarbon pretreatment steps can be used to preparethe hydrocarbon for the naphtha reforming process. For example,hydrotreating may be used to remove catalyst poisons such as sulfur.Further, contacting the hydrocarbons with a massive nickel catalyst, forexample, prior to hydrotreating and reforming can also protect againstfailure of the hydrotreating system (e.g., against hydrotreatingcatalyst failure).

In some embodiments, the hydrocarbon feed stream can be processed in apreliminary reactor prior to introducing the hydrocarbon feed stream tothe first reactor, where the preliminary reactor can comprise a bed witha sulfur adsorbing material, as will be described in more detail laterherein.

In an embodiment, the first reactor can comprise a first inlet and afirst outlet, where the hydrocarbon feed stream can be introduced to thefirst reactor via the first inlet, and where the first reactor effluentcan be recovered from the first reactor via the first outlet.

In an embodiment, the first reactor can comprise an adiabatic reactor,where the first reactor can comprise a first naphtha reforming catalyst,and where at least a portion of the convertible hydrocarbons in thehydrocarbon feed stream are converted to aromatic hydrocarbons in thefirst reactor to form the first reactor effluent. As used herein, anadiabatic reactor is any reactor operated under adiabatic naphthareforming conditions. Under adiabatic naphtha reforming conditions thereis no transfer of heat through the external reactor walls or throughinternal heat transfer surfaces. Under adiabatic naphtha reformingconditions all the heat necessary for the reactor comes into the reactorwith the reactants, specifically the hydrocarbon feed stream. Adiabaticnaphtha reforming conditions are naphtha reforming reaction conditionsthat exclude heat exchange between the reactor (e.g., reforming reactor)and a heat exchange system. As will be appreciated by one of skill inthe art and with the help of this disclosure, an adiabatic reactor canhave some amount of heat exchange with its surroundings, and suchexchange does not constitute “heat exchange” as disclosed herein.

In an embodiment, the adiabatic reactor employed in the processesdescribed herein can be any conventional type of reactor that maintainsa catalyst within the reactor and can accommodate a continuous flow ofhydrocarbon. An adiabatic reactor system described herein can comprise afixed catalyst bed system, a moving catalyst bed system, a fluidizedcatalyst bed system, or combinations thereof. Suitable adiabaticreactors can include, but are not limited to, fixed bed reactorsincluding radial flow reactors, bubble bed reactors, or ebullient bedreactors. The flow of the hydrocarbon feed can be upward, downward, orradially through the adiabatic reactor.

In an embodiment, the first reactor can comprise a radial flow reactor(e.g., an adiabatic radial flow reactor). In an embodiment, theadiabatic reactor can comprise a fixed bed radial flow reactor.Generally, a radial flow reactor is a cylindrical vessel comprising anexternal reactor shell and a catalyst bed disposed inside the reactorshell. The radial flow reactor usually comprises a center-pipe in thecenter of the reactor and an outer annulus formed by scallops, the twoforming an annular or radial bed, causing the gas to flow between acenter-pipe and the outer annulus separated from the external reactorshell by the scallops. Radial flow reactors can be centrifugal (CF) flowtype reactors, where a gas is fed to the center-pipe and it flows fromthe center-pipe outwards, through the annular catalyst bed to the outerannulus; or centripetal (CP) flow type reactors, where a gas is fed tothe outer annulus and it flows from the outer annulus inwards, throughthe annular catalyst bed to the center-pipe. Radial flow reactors have ahigh flow cross-sectional area per catalyst bed volume, and as such canachieve high throughput without increased gas velocity. In someembodiments, the catalyst bed can be relatively thin, and thus candisplay a low pressure drop.

In an embodiment, the first reactor can comprise a naphtha reformingcatalyst (e.g., a first naphtha reforming catalyst). For purposes of thedisclosure herein, a naphtha reforming catalyst refers to any catalystsuitable for carrying out a naphtha reforming process. As will beappreciated by one of skill in the art, and with the help of thisdisclosure, a suitable naphtha reforming catalyst is capable ofconverting at least a portion of the convertible hydrocarbons such asaliphatic, alicyclic, and/or naphthenic hydrocarbons (e.g., non-aromatichydrocarbons) in a hydrocarbon feed stream to aromatic hydrocarbons. Anycatalyst capable of carrying out naphtha reforming reactions may be usedalone or in combination with additional catalytic materials in thereactors. Suitable naphtha reforming catalysts may include alumina basednaphtha reforming catalysts or zeolitic naphtha reforming catalysts. Inan aspect, the alumina based naphtha reforming catalysts can comprise abifunctional catalyst, such as a Pt/Al₂O₃ catalyst. In another aspect,the zeolitic naphtha reforming catalysts can comprise a zeoliticreforming catalyst, such as a bound Pt/K L-Zeolite.

In an embodiment, the naphtha reforming catalyst is a zeolitic naphthareforming catalyst. A suitable zeolitic naphtha reforming catalyst maycomprise a bound zeolite support (e.g., silica bound zeolite), at leastone group VIII metal, IB metal, or combinations thereof, and one or morehalides. Suitable halides include chloride, fluoride, bromide, iodide,or combinations thereof. Suitable Group VIII metals include iron,cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium,platinum, or combinations thereof. Suitable Group IB metals includecopper, silver, gold, or combinations thereof. Examples of naphthareforming catalysts suitable for use with the catalytic reactor systemsdescribed herein are AROMAX® Catalysts available from the ChevronPhillips Chemical Company LP of The Woodlands, Tex., and those discussedin U.S. Pat. Nos. 6,190,539, 6,812,180, 7,153,801, and 8,263,518 each ofwhich is incorporated by reference herein in its entirety.

In an embodiment, the naphtha reforming catalyst can comprise a zeoliticnaphtha reforming catalyst, e.g., a naphtha reforming catalystcomprising a group VIII metal on a zeolitic support. Zeolitic reformingcatalysts can generally include any inorganic oxide as the binder forthe zeolite. The zeolite of the zeolitic reforming catalyst may includebound large pore aluminosilicates (zeolites); and/or large porealuminosilicates such as a zeolite having an effective pore diameter ofabout 7 angstroms or larger, which can include, but are not limited to,L-zeolite (LTL), Y-zeolite, mordenite, omega zeolite, beta zeolite,Mazzite (MAZ), and the like. Suitable binders are inorganic oxides whichcan include, but are not limited to, silica, alumina, clays, titania,and magnesium oxide. In an embodiment, the support comprises a boundzeolitic support. In an aspect, the reforming catalyst can be a silicabound zeolite.

The reforming catalyst may be a dual-function reforming catalystcontaining a metallic hydrogenation-dehydrogenation component on aninorganic oxide support which provides acid sites for cracking andisomerization. Examples of suitable inorganic oxide supports for thedual-function reforming catalysts include one or more inorganic oxidessuch as alumina, silica, titania, magnesia, zirconia, chromia, thoria,boria, spinels (e.g., MgAl₂O₄, FeAl₂O₄, ZnAl₂O₄, CaAl₂O₄), andsynthetically prepared or naturally occurring clays and silicates. Insome aspects, the inorganic oxide supports for the dual-functionreforming catalysts may be acid-treated.

The term “zeolite” generally refers to a group of hydrated, crystallinealuminosilicates. These zeolites exhibit a network of SiO₄ and AlO₄tetrahedra in which aluminum and silicon atoms are crosslinked in athree-dimensional framework by sharing oxygen atoms. In the framework,the mole ratio of oxygen atoms to the total of aluminum and siliconatoms may be equal to about 2. The framework exhibits a negativeelectrovalence that typically is balanced by the inclusion of cationswithin the crystal such as metals, alkali metals, alkaline earth metals,or hydrogen.

Zeolitic naphtha reforming catalysts based on zeolitic supportscomprising L-type zeolites are a sub-group of zeolitic catalysts.Typical L-type zeolites contain mole ratios of oxides in accordance withthe formula: M_(2/n)O.Al₂O₃.xSiO₂.yH₂O where “M” designates at least oneexchangeable cation such as barium, calcium, cerium, lithium, magnesium,potassium, sodium, strontium, and zinc as well as non-metallic cationslike hydronium and ammonium ions which may be replaced by otherexchangeable cations without causing a substantial alteration of thebasic crystal structure of the L-type zeolite. The “n” in the formularepresents the valence of “M”, “x” is 2 or greater; and “y” is thenumber of water molecules contained in the channels or interconnectedvoids with the zeolite. Bound zeolitic supports comprising potassiumL-type zeolites, or KL zeolites, have been found to be particularlydesirable. The term “KL zeolite” as used herein refers to L-typezeolites in which the principal cation M incorporated in the zeolite ispotassium. A KL zeolite may be cation-exchanged or impregnated withanother metal and one or more halides to produce a platinum-impregnated,halided zeolite or a KL supported Pt-halide zeolite catalyst.

In an embodiment, the at least one Group VIII metal is platinum. Inanother embodiment, the at least one Group VIII metal is platinum andthe Group IB metal is gold. In an embodiment, the at least one GroupVIII metal is platinum and rhenium. The platinum and optionally one ormore halides may be added to the zeolitic support by any suitablemethod, for example via impregnation with a solution of aplatinum-containing compound and one or more halide-containingcompounds. For example, the platinum-containing compound can be anydecomposable platinum-containing compound. Examples of such compoundsinclude, but are not limited to, ammonium tetrachloroplatinate,chloroplatinic acid, diammineplatinum (II) nitrite,bis-(ethylenediamine)platinum (II) chloride, platinum (II)acetylacetonate, dichlorodiammine platinum, platinum (II) chloride,tetraammineplatinum (II) hydroxide, tetraammineplatinum chloride, andtetraammineplatinum (II) nitrate.

In an embodiment, the naphtha reforming catalyst comprises a Group VIIImetal; on a bound zeolitic support and at least one ammonium halidecompound. The ammonium halide compound may comprise one or morecompounds represented by the formula N(R)₄X, where X is a halide andwhere R represents a hydrogen or a substituted or unsubstituted carbonchain molecule having 1-20 carbons, where each R may be the same ordifferent. In an embodiment, R is selected from the group consisting ofmethyl, ethyl, propyl, butyl, and combinations thereof, morespecifically methyl. Examples of suitable ammonium compounds arerepresented by the formula N(R)₄X and include ammonium chloride,ammonium fluoride, and tetraalkylammonium halides such astetramethylammonium chloride, tetramethylammonium fluoride,tetraethylammonium chloride, tetraethylammonium fluoride,tetrapropylammonium chloride, tetrapropylammonium fluoride,tetrabutylammonium chloride, tetrabutylammonium fluoride,methyltriethylammonium chloride, methyltriethylammonium fluoride, andcombinations thereof.

In an embodiment, the naphtha reforming catalyst can comprise platinumon a bound zeolitic support, such as for example platinum on silicabound KL-zeolite.

The naphtha reforming catalyst can be employed in any of the formsand/or profiles known to the art. The naphtha reforming catalyst can beemployed in any desired catalyst shape. Desirable shapes include pills,pellets, granules, broken fragments, or extrudates with any profileknown in the art. The naphtha reforming catalyst can be disposed withina reaction zone (e.g., in a fixed bed reactor, or in a moving bedreactor), disposed within a catalyst zone, and a hydrocarbon feed streammay be passed therethrough in the liquid, vapor, or mixed phase, and ineither upward or downward, or inward or outward flow (e.g., radialflow).

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can further comprise heating the hydrocarbon feedstream in a first furnace prior to introducing the hydrocarbon feedstream to the first reactor. Generally, the first furnace can be locatedupstream of the first reactor. In an embodiment, the first furnace canbe a process heater that brings a feed to a required temperature for anintended reaction. Generally, a process heater (e.g., a fired heater)can be a direct-fired heat exchanger that uses the hot gases ofcombustion to raise the temperature of a feed flowing through one ormore coils and/or tubes aligned throughout the process heater. In anembodiment, the first furnace can comprise any suitable furnace capableof raising the temperature of a feed stream (e.g., hydrocarbon feedstream) to achieve a desired inlet temperature to the reactorimmediately downstream of the furnace. The temperature of the feedstream (e.g., hydrocarbon feed stream) needs to be raised so that thenaphtha reforming reactions proceed in the subsequent reactor (e.g.,first reactor), which is generally needed due to the endothermic natureof the reforming reactions.

In an embodiment, the first furnace can comprise tubes disposed therein,where the tubes can be in fluid communication with the first inlet ofthe first reactor, and where the first furnace is configured to heat ahydrocarbon feed stream (e.g., heat the tubes that the hydrocarbon feedstream is flowing through) prior to the hydrocarbon feed stream enteringthe first inlet of the first reactor.

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can further comprise heating the hydrocarbon feedstream in a heat exchanger prior to introducing the hydrocarbon feedstream to the first reactor. The hydrocarbon feed stream can exchangeheat with downstream reactor effluents (e.g., first reactor effluent,second reactor effluent, feed effluent heat exchanger effluent, etc.) toincrease a temperature of the hydrocarbon feed stream, while decreasinga temperature of the downstream reactor effluent.

In an embodiment, the hydrocarbon feed stream can be heated whilecooling the second reactor effluent by heat exchange between the secondreactor effluent with the hydrocarbon feed stream.

In some embodiments, a method of carrying out a naphtha reformingprocess as disclosed herein can further comprise heating the hydrocarbonfeed stream in a heat exchanger prior to introducing the hydrocarbonfeed stream to the first furnace to yield a preheated hydrocarbon feedstream, and further heating the preheated hydrocarbon feed stream in afirst furnace prior to introducing the hydrocarbon feed stream to thefirst reactor.

In general, the naphtha reforming reactions occurs under processconditions that thermodynamically favor the dehydrocyclization reactionsand limit undesirable hydrocracking reactions, whether the naphthareforming reactions are carried out in an adiabatic reactor, anisothermal reactor, or both. The naphtha reforming reactions can becarried out using any conventional naphtha reforming conditions, and maybe carried out at reactor inlet temperatures ranging from about 600° F.(316° C.) to about 1,000° F. (538° C.), alternatively from about 650° F.(343° C.) to about 1,000° F. (538° C.), alternatively from about 700° F.(371° C.) to about 950° F. (510° C.), alternatively from about 750° F.(399° C.) to about 950° F. (510° C.), or alternatively from about 800°F. (427° C.) to about 950° F. (510° C.). Reaction pressures can rangefrom about atmospheric pressure to about 300 psig (2.07 MPa),alternatively from about 25 psig (0.17 MPa) to about 300 psig (2.07MPa), or alternatively from about 30 psig (0.21 MPa) to about 100 psig(0.69 MPa). The mole ratio of hydrogen to hydrocarbon in the hydrocarbonfeed stream is normally between about 0.1:1 and about 10:1,alternatively from about 0.5:1 to about 5.0:1, or alternatively fromabout 1:1 to about 3:1. The liquid hourly space velocity (LHSV) for thehydrocarbon feed stream over the naphtha reforming catalyst (e.g.,aromatization catalyst) is from about 0.5 hr⁻¹ to about 20 hr⁻¹, oralternatively from about 0.50 hr⁻¹ to about 5.0 hr⁻¹, based on thenaphtha reforming catalyst in a reaction zone.

In an embodiment, an operating temperature in the first reactor does notexceed about 1,000° F. (538° C.), alternatively about 975° F. (524° C.),or alternatively about 950° F. (510° C.). In such embodiment, the firstinlet of the first reactor can be configured to be maintained at atemperature of less than about 1,000° F. (538° C.), alternatively lessthan about 975° F. (524° C.), or alternatively less than about 950° F.(510° C.).

In an embodiment, a second or subsequent (e.g., downstream) reactor cancomprise a second inlet and a second outlet, where the first reactoreffluent can be introduced to the second reactor via the second inlet,and where the second reactor effluent can be recovered from the secondreactor via the second outlet. In an embodiment, the second inlet of thesecond reactor can be in fluid communication with the first outlet ofthe first reactor. The first reactor effluent can be recovered from thefirst reactor via the first outlet, and then can be passed to the secondreactor via the second inlet.

In an embodiment, the second reactor can comprise an isothermal reactor(e.g., reactor operating under approximately isothermal naphthareforming conditions), where the second reactor can comprise a secondnaphtha reforming catalyst and where at least a portion of theconvertible hydrocarbons in the first reactor effluent can be convertedto an additional amount of the aromatic hydrocarbons in the secondreactor to form the second reactor effluent. Generally, the term“isothermal” refers to a fairly constant temperature. As will beappreciated by one of skill in the art, and with the help of thisdisclosure, isothermal reactors are subjected to external heat exchangeto ensure a constant operating temperature, for example isothermalreactors are either heated or cooled (depending on the type of thereaction that is performed inside the reactor).

In an embodiment, the second reactor can comprise a naphtha reformingcatalyst (e.g., a second naphtha reforming catalyst). The second naphthareforming catalyst can comprise any suitable naphtha reforming catalyst,for example a naphtha reforming catalyst as described previously hereinfor the first naphtha reforming catalyst. In some embodiments, the firstnaphtha reforming catalyst and the second naphtha reforming catalyst canbe the same. In other embodiments, the first naphtha reforming catalystand the second naphtha reforming catalyst can be different.

In some embodiments, the first naphtha reforming catalyst, the secondnaphtha reforming catalyst, or both can comprise a zeolitic naphthareforming catalyst, for example platinum on a bound zeolitic support,such as platinum on silica bound KL-zeolite.

As used herein, an isothermal reactor is a reactor that is characterizedby a fairly constant temperature within the catalyst bed that undergoesa reaction with a feed stream or reactant stream in the isothermalreactor (e.g., within a narrow temperature range, such as within atemperature difference of 50° C., 40° C., 30° C., 20° C., or 10° C.).Further, for purposes of the disclosure herein, an isothermal reactorcan be defined as a reactor operating at a temperature above a certainthreshold, such as a reactor operating at a temperature capable ofsustaining a naphtha reforming reactions (e.g., a reactor operating at atemperature above the activation temperature for the naphtha reformingreactions).

In an embodiment, an operating temperature in the second reactor doesnot exceed about 1,000° F. (538° C.), alternatively about 975° F. (524°C.), or alternatively about 950° F. (510° C.). In an embodiment, thesecond inlet can be configured to be maintained at a temperature of lessthan about 1,000° F. (538° C.), alternatively less than about 975° F.(524° C.), or alternatively less than about 950° F. (510° C.).

In an embodiment, operating under isothermal naphtha reformingconditions in the second reactor can comprise operating at a temperatureequal to or greater than about 800° F. (425° C.), alternatively equal toor greater than about 850° F. (450° C.), or alternatively equal to orgreater than about 925° F. (500° C.).

In an embodiment, one or more temperature indicators (e.g.,thermocouples) could be incorporated into some of the tubes of theplurality of tubes of the second reactor (e.g., isothermal reactor),such that an internal tube temperature could be monitored. In anembodiment, temperature indicators can be incorporated into about 1% toabout 5% of the total number of tubes of the plurality of tubes in theisothermal reactor.

In an embodiment, the second reactor can comprise one or more tubesdisposed within a reactor furnace, where each tube can comprise thesecond naphtha reforming catalyst. In an embodiment, the second reactorcan comprise a plurality of tubes with particles of the second naphthareforming catalyst disposed therein, where the plurality of tubes isdisposed within a reactor furnace. The first reactor effluent can enterthe plurality of tubes comprising the second naphtha reforming catalyst,and undergoes the naphtha reforming reactions as it travels within thetubes to produce the second reactor effluent which exits the tubes andis recovered from the second reactor. Generally, the reactor furnace cancomprise any suitable furnace, such as a process heater (e.g., a firedheater) housing the plurality of tubes comprising the second naphthareforming catalyst, where the reactor furnace can be a direct-fired heatexchanger that uses the hot gases and radiant energy of combustion toraise and maintain the temperature of a feed flowing through andreacting within the plurality of tubes housed therein. In an embodiment,the plurality of tubes comprising the second naphtha reforming catalystdisposed therein can be heated by burners in the reactor furnace.

In an embodiment, the first reactor effluent can be heated within thesecond reactor, where heating the first reactor effluent within thesecond reactor occurs during the conversion of at least a portion of theconvertible hydrocarbons in the first reactor effluent to an additionalamount of the aromatic hydrocarbons in the second reactor to form thesecond reactor effluent. As will be appreciated by one of skill in theart, and with the help of this disclosure, in order to perform anendothermic reaction (e.g., naphtha reforming reactions) underisothermal conditions (e.g., isothermal naphtha reforming conditions),the reaction zone (e.g., reactants such as the convertible hydrocarbonswithin a reaction zone) has to be supplied with heat to maintain thetemperature within a desired range, or above a desired temperature(e.g., above the activation temperature for the naphtha reformingreactions).

In some embodiments, the reactor furnace can comprise a radiant zone anda convection zone (e.g., a non-radiant zone). The radiant zone of thereactor furnace comprises the zone where the firing of a plurality ofburners produces radiant energy and a hot flue gas. The plurality oftubes can be heated by direct exposure to the radiant energy and the hotflue gas in the radiant zone of the reactor furnace. As will beappreciated by one of skill in the art, and with the help of thisdisclosure, the primary type of heat transfer in the radiant zone heatedby burners is radiative heat transfer, although some convective heattransfer also occurs in the radiant zone. The hot flue gas is dischargedfrom the radiant zone via the convection zone into the atmosphere. Here,the hot flue gas is utilized as heat transfer medium in the convectionzone. The convection zone of the reactor furnace therefore has at leastone heat exchanger for heating the first reactor effluent. Theconvection zone of the reactor furnace may have other heat exchangers toheat other streams within the process to maximize heat integration. Forexample, preheating hydrocarbon feed streams or for the production ofsteam. As will be appreciated by one of skill in the art, and with thehelp of this disclosure, the primary type of heat transfer in theconvection zone is convective heat transfer, although some radiativeheat transfer may also occur in the convection zone.

The convection zone of the reactor furnace comprises the zone of thereactor furnace where the first reactor effluent travels through priorto entering the plurality of tubes comprising particles of the secondnaphtha reforming catalyst disposed therein. The convection zone allowsthe first reactor effluent to capture available heat, thereby increasingthe temperature of the first reactor effluent, prior to the firstreactor effluent entering the second reactor (e.g., isothermal reactor).The second reactor effluent that exits the plurality of tubes comprisingparticles of the second naphtha reforming catalyst disposed therein canalso travel through the convection zone of the reactor furnace prior torecovering the second reactor effluent from the second reactor (e.g.,isothermal reactor). The convection zone allows the second reactoreffluent to capture available heat, thereby increasing the temperatureof the second reactor effluent, prior to the second reactor effluentbeing recovered from the second reactor (e.g., isothermal reactor). Theheat captured by the second reactor effluent can be used for heattransfer in a heat exchanger, as described in more detail later herein.

In some embodiments, the first reactor effluent can be heated prior topassing the first reactor effluent into the second reactor. In anembodiment, heating the first reactor effluent comprises heating thefirst reactor effluent within heat exchange tubes disposed within theconvection zone of the reactor furnace, where the heat exchange tubesare in fluid communication with the second inlet of the second reactor.The flow of first reactor effluent can be distributed between aplurality of heat exchange tubes in the convection zone, to allow formore efficient heat transfer to the first reactor effluent.

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can further comprise heating the first reactoreffluent in a second furnace prior to introducing the first reactoreffluent to the second reactor. Generally, the second furnace can belocated upstream of the second reactor (e.g., upstream of the reactorfurnace). In an embodiment, the second furnace can be a process heaterthat brings a feed to a required temperature for an intended reaction,such as for example a process heater as described herein for the firstfurnace. In an embodiment, the second furnace can comprise any suitablefurnace capable of raising the temperature of a feed stream (e.g., firstreactor effluent) to achieve a desired inlet temperature to the reactorimmediately downstream of the second furnace (e.g., second reactor). Thetemperature of the feed stream (e.g., first reactor effluent) can beraised so that the naphtha reforming reactions proceed in the subsequentreactor (e.g., second reactor), which is generally needed due to theendothermic nature of the naphtha reforming reactions.

In an embodiment, the second furnace can comprise heat exchange tubesdisposed therein, where the heat exchange tubes can be in fluidcommunication with the second inlet of the second reactor, and where thesecond furnace is configured to heat the first reactor effluent stream(e.g., heat the heat exchange tubes that the first reactor effluentstream is flowing through) prior to the first reactor effluent streamentering the second inlet of the second reactor.

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can comprise heating the first reactor effluent in aheat exchanger prior to introducing the first reactor effluent to thesecond reactor. The first reactor effluent can exchange heat withdownstream reactor effluents (e.g., second reactor effluent) to increasea temperature of the first reactor effluent, while decreasing atemperature of the downstream reactor effluent.

In an embodiment, the first reactor effluent can be heated while coolingthe second reactor effluent by heat exchange between the second reactoreffluent and the first reactor effluent. In an embodiment, a heatexchanger can be configured to provide thermal contact between a fluidpassing through the second outlet of the second reactor and a fluidpassing into the second inlet of the second reactor.

In some embodiments, heating the first reactor effluent can comprisesheating the first reactor effluent while cooling the second reactoreffluent by heat exchange in a feed effluent heat exchanger to produce afeed effluent heat exchanger effluent, where the feed effluent heatexchanger effluent is the cooled second reactor effluent. The feedeffluent heat exchanger effluent can be further used in another heatexchanger, for example for heating the hydrocarbon feed stream.

In an embodiment, a heat exchanger can be configured to provide thermalcontact between a fluid passing through the second outlet of the secondreactor and a fluid passing through the first outlet of the firstreactor. In such embodiment, the fluid passing through the first outletof the first reactor can be subjected to a first heating step in theheat exchanger, and subsequently to any other desired heating steps,such as for example in a furnace (e.g., a second furnace) and/or in theconvection zone of the reactor furnace, prior to introducing the fluidinto the second inlet of the second reactor.

In some embodiments, a method of carrying out a naphtha reformingprocess as disclosed herein can further comprise heating the firstreactor effluent in a heat exchanger prior to introducing the firstreactor effluent to the second furnace to yield a preheated firstreactor effluent, and further heating the preheated first reactoreffluent in a second furnace and/or a convection zone of the reactorfurnace prior to introducing the first reactor effluent to the secondreactor.

In an embodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can further comprise a third reactorcomprising a third inlet and a third outlet, where the third reactor isconfigured to operate as an adiabatic reactor, and where the thirdreactor comprises a third reforming catalyst. The third reformingcatalyst can be any suitable naphtha reforming catalyst described hereinfor the first naphtha reforming catalyst, the second naphtha reformingcatalyst or both. In some embodiments, the third reforming catalyst canbe the same as the first naphtha reforming catalyst or the secondnaphtha reforming catalyst. In other embodiments, the third reformingcatalyst can be different than the first naphtha reforming catalyst orthe second naphtha reforming catalyst. In an embodiment, the thirdreforming catalyst can comprise a zeolitic naphtha reforming catalyst.In an embodiment, the third reactor can be a radial flow reactor.

In an aspect, a radial flow reactor of the type disclosed herein cancomprise a naphtha reforming catalyst having a catalyst particle size offrom about 0.01 inches (0.25 mm) to about 0.5 inches (12.7 mm),alternatively from about 0.05 inches (1.27 mm) to about 0.35 inches(8.89 mm), or alternatively from about 0.0625 inches (1.59 mm) to about0.25 inches (6.35 mm).

In an embodiment, the third outlet of the third reactor can be in fluidcommunication with the first inlet of the first reactor. In someembodiments, a raw hydrocarbon feed stream can be introduced to thethird reactor via the third inlet. A temperature in the third reactorcan be suitable for the naphtha reforming catalyst in the third reactorto absorb sulfur (e.g., sulfur containing compounds) that might bepresent in the hydrocarbon feed stream. The catalyst in the thirdreactor coupled in series with the first reactor can be used as a sulfuradsorbing material to protect the catalyst in the remainder of thereactors in the reactor system for carrying out a naphtha reformingprocess as disclosed herein. The third reactor may allow for theelimination of a separate sulfur converter adsorber (SCA), thussimplifying the process and saving the capital and operating costsassociated with the operation of a sulfur converter adsorber.

In some embodiments, a reactor system for carrying out a naphthareforming process as disclosed herein does not comprise a sulfurconverter adsorber. Sulfur adsorbing systems will be described in moredetail later herein.

In an embodiment, a third reactor effluent comprising the hydrocarbonfeed stream can be recovered from the third reactor via the third outletof the third reactor. A concentration of sulfur (e.g., sulfur containingcompounds) in the hydrocarbon feed stream can be lower than aconcentration of sulfur (e.g., sulfur containing compounds) in the rawhydrocarbon feed stream.

In some embodiments, an increase in an outlet reactor temperature in thethird reactor could indicate a loss of activity for an endothermicreaction, e.g., could indicate that the naphtha reforming catalyst inthe third reactor is spent and should be rejuvenated. Alternatively, asulfur (e.g., sulfur containing compounds) concentration of the thirdreactor effluent could be monitored to indicate when the third reformingcatalyst would require to be rejuvenated.

An embodiment of a general naphtha reforming process 100 is shown inFIG. 1. At the inlet of the process, the hydrocarbon feed stream is fedthrough line 102. The hydrocarbon feed stream passing through line 102can be heated in a first furnace 108 to increase the temperature of thehydrocarbon feed stream. The heated hydrocarbon feed stream passingthrough line 109 can be introduced to a first reactor 110, where thefirst reactor 110 can be an adiabatic radial flow reactor comprising acatalyst bed 112 disposed therein, and where the catalyst bed 112 cancomprise a first naphtha reforming catalyst. The first reactor 110 caninclude any of the adiabatic reactors described herein. At least aportion of the convertible hydrocarbons in the hydrocarbon feed streamcan be converted to aromatic hydrocarbons in the first reactor 110 toform a first reactor effluent. The first reactor effluent passingthrough line 116 can be heated in a second furnace 120 to increase thetemperature of the first reactor effluent. The heated first reactoreffluent passing through line 122 can be introduced to a second reactor140, where the second reactor 140 can operate under isothermal naphthareforming conditions. The second reactor 140 can include any of theisothermal reactors described herein. The second reactor 140 cancomprise a plurality of tubes 142 having a second naphtha reformingcatalyst disposed therein, where the plurality of tubes 142 can bedisposed within a reactor furnace 150. The first naphtha reformingcatalyst and the second naphtha reforming catalyst can be the same ordifferent. At least an additional portion of the convertiblehydrocarbons in the first reactor effluent can be converted to aromatichydrocarbons in the second reactor 140 to form a second reactor effluent144. As will be appreciated by one of skill in the art, and with thehelp of this disclosure, although the isothermal tubes are depicted inthe Figures herein as being grouped into bundles (e.g., two tubebundles), the isothermal tubes can be disposed in any suitableconfiguration, such as in a suitable matrix pattern of tubes (e.g.,which could be larger tubes), spaced out for example in a triangular orsquare grid pattern. Further, and as will be appreciated by one of skillin the art, and with the help of this disclosure, although theisothermal tubes are depicted in the Figures herein as being groupedinto two bundles, any suitable number of tube bundles can be used, suchas 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more tube bundles.

An embodiment of another naphtha reforming process 200 is shown in FIG.2. At the inlet of the process, the hydrocarbon feed stream is fedthrough line 202. The hydrocarbon feed stream passing through line 202can be passed through a first heat exchanger 204 to preheat thehydrocarbon feed stream. The hydrocarbon feed stream passing throughline 202 can capture heat from a second reactor effluent 246 in thefirst heat exchanger 204 to produce a preheated hydrocarbon feed streampassing through line 206, where a temperature of the second reactoreffluent 246 is greater than a temperature of the hydrocarbon feedstream passing through line 202, and where the second reactor effluent246 gives away heat and produces a second reactor effluent 248.

The preheated hydrocarbon feed stream passing through line 206 can beheated in a first furnace 208 to further increase the temperature of thehydrocarbon feed stream. For example, the preheated hydrocarbon feedstream passing through line 206 can be heated in a first furnace 208 toa naphtha reforming temperature. The heated hydrocarbon feed streampassing through line 209 can be introduced to a first reactor 210, wherethe first reactor 210 can be an adiabatic radial flow reactor comprisinga catalyst bed 212 disposed therein, and where the catalyst bed 212 cancomprise a first naphtha reforming catalyst. The first reactor 210 caninclude any of the adiabatic reactors described herein. At least aportion of the convertible hydrocarbons in the hydrocarbon feed streamcan be converted to aromatic hydrocarbons in the first reactor 210 toform a first reactor effluent passing through line 216.

The first reactor effluent passing through line 216 can be passedthrough a second heat exchanger 217 to preheat the first reactoreffluent. The first reactor effluent passing through line 216 cancapture heat from a second reactor effluent 244 in the second heatexchanger 217 to produce a preheated first reactor effluent passingthrough line 218, where a temperature of the second reactor effluent 244is greater than a temperature of the first reactor effluent passingthrough line 216, and where the second reactor effluent 244 gives awayheat and produces a second reactor effluent 246.

The preheated first reactor effluent passing through line 218 can beheated in a second furnace 220 to further increase the temperature ofthe first reactor effluent. For example, the preheated first reactoreffluent passing through line 218 can be heated in a second furnace 220to a naphtha reforming temperature. The heated first reactor effluentpassing through line 222 can be introduced to a second reactor 240,where the second reactor 240 can operate under isothermal naphthareforming conditions. The second reactor 240 can include any of theisothermal reactors described herein. The second reactor 240 cancomprise a plurality of tubes 242 having a second naphtha reformingcatalyst disposed therein, where the plurality of tubes 242 can bedisposed within a reactor furnace 250. The first naphtha reformingcatalyst and the second naphtha reforming catalyst can be the same ordifferent. At least an additional portion of the convertiblehydrocarbons in the first reactor effluent can be converted to aromatichydrocarbons in the second reactor 240 to form a second reactor effluent244.

The second reactor effluent 244 can exchange heat with the first reactoreffluent in the second heat exchanger 217 to produce a second reactoreffluent 246, where a temperature of the second reactor effluent 246 islower than a temperature of the second reactor effluent 244. The secondreactor effluent 246 can further exchange heat with the hydrocarbon feedstream in the first heat exchanger 204 to produce a second reactoreffluent 248, where a temperature of the second reactor effluent 248 islower than a temperature of the second reactor effluent 246.

An embodiment of yet another naphtha reforming process 300 is shown inFIG. 3. At the inlet of the process, the hydrocarbon feed stream is fedthrough line 302. The hydrocarbon feed stream passing through line 302can be passed through a first heat exchanger 304 to preheat thehydrocarbon feed stream. The hydrocarbon feed stream passing throughline 302 can capture heat from a second reactor effluent 346 in thefirst heat exchanger 304 to produce a preheated hydrocarbon feed streampassing through line 306, where a temperature of the second reactoreffluent 346 is greater than a temperature of the hydrocarbon feedstream passing through line 302, and where the second reactor effluent346 gives away heat and produces a second reactor effluent 348.

The preheated hydrocarbon feed stream passing through line 306 can beheated in a first furnace 308 to further increase the temperature of thehydrocarbon feed stream. For example, the preheated hydrocarbon feedstream passing through line 306 can be heated in a first furnace 308 toa naphtha reforming temperature. The heated hydrocarbon feed streampassing through line 309 can be introduced to a first reactor 310, wherethe first reactor 310 can be an adiabatic radial flow reactor comprisinga catalyst bed 312 disposed therein, and where the catalyst bed 312 cancomprise a first naphtha reforming catalyst. The first reactor 310 caninclude any of the adiabatic reactors described herein. At least aportion of the convertible hydrocarbons in the hydrocarbon feed streamcan be converted to aromatic hydrocarbons in the first reactor 310 toform a first reactor effluent passing from the first reactor in line316.

The first reactor effluent passing through line 316 can be passedthrough a second heat exchanger 317 to preheat the first reactoreffluent. The first reactor effluent passing through line 316 cancapture heat from a second reactor effluent 344 in the second heatexchanger 317 to produce a preheated first reactor effluent passingthrough line 318, where a temperature of the second reactor effluent 344is greater than a temperature of the first reactor effluent passingthrough line 316, and where the second reactor effluent 344 gives awayheat and produces a second reactor effluent 346.

The preheated first reactor effluent passing through line 318 can beheated in a convection zone 330 of a reactor furnace 350 to furtherincrease the temperature of the first reactor effluent. For example, thepreheated first reactor effluent passing through line 318 can be heatedin a convection zone 330 of a reactor furnace 350 to a naphtha reformingtemperature. The heated first reactor effluent passing through line 322can be introduced to a second reactor 340, where the second reactor 340can operate under isothermal naphtha reforming conditions. The secondreactor 340 can include any of the isothermal reactors described herein.The second reactor 340 can comprise a plurality of tubes 342 having asecond naphtha reforming catalyst disposed therein, where the pluralityof tubes 342 can be disposed within a radiant zone of the reactorfurnace 350. The first naphtha reforming catalyst and the second naphthareforming catalyst can be the same or different. At least an additionalportion of the convertible hydrocarbons in the first reactor effluentcan be converted to aromatic hydrocarbons in the second reactor 340 toform a second reactor effluent 344.

The second reactor effluent 344 can exchange heat with the first reactoreffluent in the second heat exchanger 317 to produce a second reactoreffluent 346, where a temperature of the second reactor effluent 346 islower than a temperature of the second reactor effluent 344. The secondreactor effluent 346 can further exchange heat with the hydrocarbon feedstream in the first heat exchanger 304 to produce a second reactoreffluent 348, where a temperature of the second reactor effluent 348 islower than a temperature of the second reactor effluent 346.

An embodiment of still yet another naphtha reforming process 400 isshown in FIG. 4. At the inlet of the process, the hydrocarbon feedstream is fed through line 402. The hydrocarbon feed stream passingthrough line 402 can be passed through a first heat exchanger 404 topreheat the hydrocarbon feed stream. The hydrocarbon feed stream passingthrough line 402 can capture heat from an isothermal reactor effluent446 in the first heat exchanger 404 to produce a preheated hydrocarbonfeed stream passing through line 406, where a temperature of theisothermal reactor effluent 446 is greater than a temperature of thehydrocarbon feed stream passing through line 402, and where theisothermal reactor effluent 446 gives away heat and produces anisothermal reactor effluent 448.

The preheated hydrocarbon feed stream passing through line 406 can beheated in a first furnace 408 to further increase the temperature of thehydrocarbon feed stream. For example, the preheated hydrocarbon feedstream passing through line 406 can be heated in a first furnace 408 toa naphtha reforming temperature. A first portion 409 a of the heatedhydrocarbon feed stream passing through line 409 can be introduced to afirst adiabatic reactor 410, and a second portion 409 b of the heatedhydrocarbon feed stream passing through line 409 can be introduced to asecond adiabatic reactor 411. The first adiabatic reactor 410 and/or thesecond adiabatic reactor 411 can include any of the adiabatic reactorsdescribed herein. The first adiabatic reactor 410 can be an adiabaticradial flow reactor comprising a first catalyst bed 412 disposedtherein, where the first catalyst bed 412 can comprise a first naphthareforming catalyst. The second adiabatic reactor 411 can be an adiabaticradial flow reactor comprising a second catalyst bed 413 disposedtherein, where the second catalyst bed 413 can comprise a first naphthareforming catalyst. The first naphtha reforming catalyst of the firstadiabatic reactor 410 and the first naphtha reforming catalyst of thesecond adiabatic reactor 411 can be the same or different. In anembodiment, the first naphtha reforming catalyst of the first adiabaticreactor 410 and the first naphtha reforming catalyst of the secondadiabatic reactor 411 are the same. At least a portion of theconvertible hydrocarbons in the hydrocarbon feed stream passing thoughline 409 a can be converted to aromatic hydrocarbons in the firstadiabatic reactor 410 to form an adiabatic reactor effluent passingthrough line 416 a. At least a portion of the convertible hydrocarbonsin the hydrocarbon feed stream passing though line 409 b can beconverted to aromatic hydrocarbons in the second adiabatic reactor 411to form an adiabatic reactor effluent passing through line 416 b. Thefirst adiabatic reactor 410 and the second adiabatic reactor 411 can beconnected (e.g., run) in parallel, and as such, when either adiabaticreactor has to be serviced, for example to restore catalyst activity,one adiabatic reactor can be disconnected and serviced, while the otheradiabatic reactor can continue the naphtha reforming process, therebyproviding for a continuous naphtha reforming process. As will beappreciated by one of skill in the art, and with the help of thisdisclosure, when one adiabatic reactor is disconnected, the overallproduction rates given by the adiabatic reactor that continues thenaphtha reforming process are reduced, although the naphtha reformingprocess remains continuous.

The adiabatic reactor effluent passing through line 416 (e.g., thecombined streams of adiabatic reactor effluent passing through lines 416a and 416 b) can be passed through a second heat exchanger 417 topreheat the adiabatic reactor effluent. The adiabatic reactor effluentpassing through line 416 can capture heat from an isothermal reactoreffluent 444 in the second heat exchanger 417 to produce a preheatedfirst adiabatic effluent passing through line 418, where a temperatureof the isothermal reactor effluent 444 is greater than a temperature ofthe adiabatic reactor effluent passing through line 416, and where theisothermal reactor effluent 444 gives away heat and produces anisothermal reactor effluent 446.

A first portion 418 a of the preheated adiabatic reactor effluentpassing through line 418 can be heated in a convection zone 430 of afirst reactor furnace 450 to further increase the temperature of theadiabatic reactor effluent. For example, the first portion 418 a of thepreheated adiabatic reactor effluent passing through line 418 can beheated in a convection zone 430 of a first reactor furnace 450 to anaphtha reforming temperature. A second portion 418 b of the preheatedadiabatic reactor effluent passing through line 418 can be heated in aconvection zone 431 of a second reactor furnace 451 to further increasethe temperature of the adiabatic reactor effluent. For example, thesecond portion 418 b of the preheated adiabatic reactor effluent passingthrough line 418 can be heated in a convection zone 431 of a secondreactor furnace 451 to a naphtha reforming temperature. The heatedadiabatic reactor effluent passing through line 422 can be introduced toa first isothermal reactor 440, where the first isothermal reactor 440can operate under isothermal naphtha reforming conditions. The heatedadiabatic reactor effluent passing through line 423 can be introduced toa second isothermal reactor 441, where the second isothermal reactor 441can operate under isothermal naphtha reforming conditions. The firstisothermal reactor 440 and/or the second isothermal reactor 441 caninclude any of the isothermal reactors described herein.

The first isothermal reactor 440 can comprise a plurality of tubes 442having a second naphtha reforming catalyst disposed therein, where theplurality of tubes 442 can be disposed within a radiant zone of thefirst reactor furnace 450. At least an additional portion of theconvertible hydrocarbons in the adiabatic reactor effluent can beconverted to aromatic hydrocarbons in the first isothermal reactor 440to form a first isothermal reactor effluent 444 a. The second isothermalreactor 441 can comprise a plurality of tubes 443 having a secondnaphtha reforming catalyst disposed therein, where the plurality oftubes 443 can be disposed within a radiant zone of the second reactorfurnace 451. The first naphtha reforming catalyst and the second naphthareforming catalyst can be the same or different. At least an additionalportion of the convertible hydrocarbons in the adiabatic reactoreffluent can be converted to aromatic hydrocarbons in the secondisothermal reactor 441 to form a second isothermal reactor effluent 444b. The first isothermal reactor 440 and the second isothermal reactor441 are connected (e.g., run) in parallel, and as such, when eitherisothermal reactor has to be serviced, for example to restore catalystactivity, one isothermal reactor can be disconnected and serviced, whilethe other isothermal reactor can continue the naphtha reforming process,thereby providing for a continuous naphtha reforming process. As will beappreciated by one of skill in the art, and with the help of thisdisclosure, when one isothermal reactor is disconnected, the overallproduction rates given by the isothermal reactor that continues thenaphtha reforming process are reduced, although the naphtha reformingprocess remains continuous.

The isothermal reactor effluent 444 (e.g., the combined streams ofisothermal reactor effluent passing through lines 444 a and 444 b) canexchange heat with the adiabatic reactor effluent in the second heatexchanger 417 to produce an isothermal reactor effluent 446, where atemperature of the isothermal reactor effluent 446 is lower than atemperature of the isothermal reactor effluent 444. The isothermalreactor effluent 446 can further exchange heat with the hydrocarbon feedstream in the first heat exchanger 404 to produce an isothermal reactoreffluent 448, where a temperature of the isothermal reactor effluent 448is lower than a temperature of the isothermal reactor effluent 446.

An embodiment of still yet another naphtha reforming process 500 isshown in FIG. 5A. At the inlet of the process, a first hydrocarbon feedstream is fed through line 501, and a second hydrocarbon feed stream isfed through line 502. The first hydrocarbon feed stream passing throughline 501 can be passed through a first heat exchanger 503 to preheat thefirst hydrocarbon feed stream. The first hydrocarbon feed stream passingthrough line 501 can capture heat from an isothermal reactor effluent546 a in the first heat exchanger 503 to produce a preheated firsthydrocarbon feed stream passing through line 505, where a temperature ofthe isothermal reactor effluent 546 a is greater than a temperature ofthe first hydrocarbon feed stream passing through line 501, and wherethe isothermal reactor effluent 546 a gives away heat and produces anisothermal reactor effluent 548 a.

The preheated first hydrocarbon feed stream passing through line 505 canbe heated in a first furnace 507 to further increase the temperature ofthe first hydrocarbon feed stream. For example, the preheated firsthydrocarbon feed stream passing through line 505 can be heated in afirst furnace 507 to a naphtha reforming temperature. The heated firsthydrocarbon feed stream passing through line 509 can be introduced to afirst adiabatic reactor 511. The first adiabatic reactor 511 can includeany of the adiabatic reactors described herein. The first adiabaticreactor 511 can be an adiabatic radial flow reactor comprising a firstcatalyst bed 513 disposed therein, where the first catalyst bed 513 cancomprise a first naphtha reforming catalyst. At least a portion of theconvertible hydrocarbons in the first hydrocarbon feed stream passingthough line 509 can be converted to aromatic hydrocarbons in the firstadiabatic reactor 511 to form an adiabatic reactor effluent passingthrough line 516 a.

The second hydrocarbon feed stream passing through line 502 can bepassed through a second heat exchanger 504 to preheat the secondhydrocarbon feed stream. The second hydrocarbon feed stream passingthrough line 502 can capture heat from an isothermal reactor effluent546 b in the second heat exchanger 504 to produce a preheated secondhydrocarbon feed stream passing through line 506, where a temperature ofthe isothermal reactor effluent 546 b is greater than a temperature ofthe second hydrocarbon feed stream passing through line 502, and wherethe isothermal reactor effluent 546 b gives away heat and produces anisothermal reactor effluent 548 b.

The preheated second hydrocarbon feed stream passing through line 506can be heated in a second furnace 508 to further increase thetemperature of the second hydrocarbon feed stream. For example, thepreheated second hydrocarbon feed stream passing through line 506 can beheated in a second furnace 508 to a naphtha reforming temperature. Theheated second hydrocarbon feed stream passing through line 510 can beintroduced to a second adiabatic reactor 512. The second adiabaticreactor 512 can include any of the adiabatic reactors described herein.The second adiabatic reactor 512 can be an adiabatic radial flow reactorcomprising a second catalyst bed 514 disposed therein, where the secondcatalyst bed 514 can comprise a first naphtha reforming catalyst. Thefirst naphtha reforming catalyst of the first adiabatic reactor 511 andthe first naphtha reforming catalyst of the second adiabatic reactor 512can be the same or different. In an embodiment, the first naphthareforming catalyst of the first adiabatic reactor 511 and the firstnaphtha reforming catalyst of the second adiabatic reactor 512 are thesame. At least a portion of the convertible hydrocarbons in the secondhydrocarbon feed stream passing though line 510 can be converted toaromatic hydrocarbons in the second adiabatic reactor 512 to form anadiabatic reactor effluent passing through line 516 b. The firstadiabatic reactor 511 and the second adiabatic reactor 512 are connected(e.g., run) in parallel, and as such, when either adiabatic reactor hasto be serviced, for example to restore catalyst activity, one adiabaticreactor can be disconnected and serviced, while the other adiabaticreactor can continue the naphtha reforming process, thereby providingfor a continuous naphtha reforming process.

The adiabatic reactor effluent passing through line 516 (e.g., thecombined streams of adiabatic reactor effluent passing through lines 516a and 516 b) can be passed through a third heat exchanger 517 to preheatthe adiabatic reactor effluent. The adiabatic reactor effluent passingthrough line 516 can capture heat from an isothermal reactor effluent544 (e.g., the combined streams of isothermal reactor effluent passingthrough lines 544 a and 544 b) in the third heat exchanger 517 toproduce a preheated adiabatic reactor effluent passing through line 518,where a temperature of the isothermal reactor effluent 544 is greaterthan a temperature of the adiabatic reactor effluent passing throughline 516, and where the isothermal reactor effluent 544 gives away heatand produces an isothermal reactor effluent 546.

A first portion 518 a of the preheated adiabatic reactor effluentpassing through line 518 can be heated in a convection zone 530 of afirst reactor furnace 545 a to further increase the temperature of theadiabatic reactor effluent. For example, the first portion 518 a of thepreheated adiabatic reactor effluent passing through line 518 can beheated in a convection zone 530 of a first reactor furnace 545 a to anaphtha reforming temperature. A second portion 518 b of the preheatedadiabatic reactor effluent passing through line 518 can be heated in aconvection zone 531 of a second reactor furnace 545 b to furtherincrease the temperature of the adiabatic reactor effluent. For example,the second portion 518 b of the preheated adiabatic reactor effluentpassing through line 518 can be heated in a convection zone 531 of asecond reactor furnace 545 b to a naphtha reforming temperature. Theheated adiabatic reactor effluent passing through line 522 can beintroduced to a first isothermal reactor 540, where the first isothermalreactor 540 can operate under isothermal naphtha reforming conditions.The heated adiabatic reactor effluent passing through line 523 can beintroduced to a second isothermal reactor 541, where the secondisothermal reactor 541 can operate under isothermal naphtha reformingconditions. The first isothermal reactor 540 and/or the secondisothermal reactor 541 can include any of the isothermal reactorsdescribed herein.

The first isothermal reactor 540 can comprise a plurality of tubes 542having a second naphtha reforming catalyst disposed therein, where theplurality of tubes 542 can be disposed within a radiant zone of thefirst reactor furnace 545 a. The first naphtha reforming catalyst andthe second naphtha reforming catalyst can be the same or different. Atleast an additional portion of the convertible hydrocarbons in theadiabatic reactor effluent can be converted to aromatic hydrocarbons inthe first isothermal reactor 540 to form a first isothermal reactoreffluent 544 a. The second isothermal reactor 541 can comprise aplurality of tubes 543 having a second naphtha reforming catalystdisposed therein, where the plurality of tubes 543 can be disposedwithin a radiant zone of the second reactor furnace 545 b. At least anadditional portion of the convertible hydrocarbons in the adiabaticreactor effluent can be converted to aromatic hydrocarbons in the secondisothermal reactor 541 to form a second isothermal reactor effluent 544b. The first isothermal reactor 540 and the second isothermal reactor541 are connected (e.g., run) in parallel, and as such, when eitherisothermal reactor has to be serviced, for example to restore catalystactivity, one isothermal reactor can be disconnected and serviced, whilethe other isothermal reactor can continue the naphtha reforming process,thereby providing for a continuous naphtha reforming process.

The isothermal reactor effluent 544 (e.g., the combined streams ofisothermal reactor effluent passing through lines 544 a and 544 b) canexchange heat with the adiabatic reactor effluent in the third heatexchanger 517 to produce an isothermal reactor effluent 546, where atemperature of the isothermal reactor effluent 546 is lower than atemperature of the isothermal reactor effluent 544. A first portion 546a of the isothermal reactor effluent 546 can further exchange heat withthe hydrocarbon feed stream in the first heat exchanger 503 to producean isothermal reactor effluent 548 a, where a temperature of theisothermal reactor effluent 548 a is lower than a temperature of theisothermal reactor effluent 546 (e.g., 546 a). A second portion 546 b ofthe isothermal reactor effluent 546 can further exchange heat with thehydrocarbon feed stream in the second heat exchanger 504 to produce anisothermal reactor effluent 548 b, where a temperature of the isothermalreactor effluent 548 b is lower than a temperature of the isothermalreactor effluent 546 (e.g., 546 b).

In an embodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can comprise a plurality of adiabaticreactors, where each adiabatic reactor of the plurality of adiabaticreactors comprises a first naphtha reforming catalyst. In someembodiments, the plurality of adiabatic reactors can comprise aplurality of radial flow reactors. The reactor system can comprise afeed header fluidly coupled to at least one of the plurality ofadiabatic reactors by one or more feed lines. The feed header can beprovided to allow the hydrocarbon feed stream to be directed to each ofthe adiabatic reactors.

In an embodiment, the reactor system can further comprise a plurality offurnaces, where each furnace of the plurality of furnaces corresponds toone of the adiabatic reactors of the plurality of adiabatic reactors andwhere each furnace of the plurality of furnaces increases a temperatureof the hydrocarbon feed stream that is communicated to a correspondingadiabatic reactor. Each furnace of the plurality of furnaces can befluidly coupled between a corresponding adiabatic reactor and the feedheader. The feed header can be provided to allow the hydrocarbon feedstream to be directed to each of the furnaces, thereby allowing for thehydrocarbon feed stream to be heated prior to introducing thehydrocarbon feed stream to a corresponding adiabatic reactor. A seriesof valves can be provided in the lines between the feed header and aninlet to each furnace.

In an embodiment, the reactor system can comprise an intermediateproduct header fluidly coupled to at least one of the plurality ofadiabatic reactors by one or more product lines. The intermediateproduct header is provided to allow for recovering or collecting thefirst reactor effluent from each adiabatic reactor of the plurality ofadiabatic reactors. A series of valves can be provided in the linesbetween the intermediate product header and outlets from each adiabaticreactor of the plurality of adiabatic reactors.

In some embodiments, the plurality of adiabatic reactors can be arrangedin series between the feed header and the intermediate product header.In other embodiments, the plurality of adiabatic reactors can bearranged in parallel between the feed header and the intermediateproduct header. In yet other embodiments, some reactors of the pluralityof adiabatic reactors can be arranged in series between the feed headerand the intermediate product header, while other reactors of theplurality of adiabatic reactors can be arranged in parallel between thefeed header and the intermediate product header.

In an embodiment, the reactor system can comprise one or more isothermalreactors, where each of the one or more isothermal reactors can comprisea second naphtha reforming catalyst. In some embodiments, the firstnaphtha reforming catalyst of the plurality of adiabatic reactors andthe second naphtha reforming catalyst of the one or more isothermalreactors can be the same. In other embodiments, the first naphthareforming catalyst of the plurality of adiabatic reactors and the secondnaphtha reforming catalyst of the one or more isothermal reactors can bedifferent. The one or more isothermal reactors can be fluidly coupled tothe intermediate product header by one or more inlet lines. Theintermediate product header can be provided to allow the hydrocarbonfeed stream to be directed to each of the isothermal reactors. A seriesof valves can be provided in the inlet lines between the intermediateproduct header and inlets to each of the one or more isothermalreactors.

In an embodiment, the reactor system can comprise an effluent headerfluidly coupled to the one or more isothermal reactors by one or moreeffluent lines. The effluent header can be provided to allow forrecovering or collecting the second reactor effluent from eachisothermal reactor. A series of valves can be provided in the linesbetween the effluent header and outlets from each isothermal reactor. Inan embodiment, a serial flow path is formed from the feed header,through one or more of the plurality of adiabatic reactors, through theintermediate product header, through at least one of the one or moreisothermal reactors, and to the effluent header.

In an embodiment, the one or more isothermal reactors can comprise aplurality of isothermal reactors. In some embodiments, the plurality ofisothermal reactors can be arranged in parallel between the intermediateproduct header and the effluent header. In other embodiments, theplurality of isothermal reactors can be arranged in series between theintermediate product header and the effluent header. In yet otherembodiments, some reactors of the plurality of isothermal reactors canbe arranged in parallel between the intermediate product header and theeffluent header, while other reactors of the plurality of isothermalreactors can be arranged in series between the intermediate productheader and the effluent header.

An embodiment of a general naphtha reforming process 550 is shown inFIG. 5B, in which additional lines (e.g., headers) are available betweenreactors to allow for a dynamic flow scheme, where individual reactorscan be isolated from the naphtha reforming process, while a continuousnaphtha reforming process can be maintained. As will be appreciated byone of skill in the art, and with the help of this disclosure, while thegeneral naphtha reforming process 550 shows two adiabatic reactors (561,562) operating in parallel, and two isothermal reactors (580, 581)operating in parallel, the concepts of the general naphtha reformingprocess 550 could be applied to any plurality of reactors (e.g.,adiabatic, and/or isothermal reactors) operating in series and/or inparallel. As used herein, the term “dynamic flow scheme” refers to theability of the hydrocarbon flow through a reactor system (e.g., areactor system as shown in FIG. 5B for carrying out the general naphthareforming process 550) to bypass any one of the adiabatic reactorsand/or any one of the isothermal reactors, for example to restorecatalytic activity in an isolated reactor, while also allowing thenaphtha reforming process to continue to operate in the remainingadiabatic reactors and isothermal reactors. A first adiabatic reactor561 and/or a second adiabatic reactor 562 can include any of theadiabatic reactors described herein. A first isothermal reactor 580and/or a second isothermal reactor 581 can include any of the isothermalreactors described herein.

In an embodiment as shown in FIG. 5B, a dynamic flow scheme is achievedby providing a feed header 552, an intermediate product header 569, aneffluent header 588, and a plurality of valves 553, 554, 567, 568, 570,571, 578, 586, 587 disposed in the lines. The valves used herein may besimple valves or may represent more complex systems such as double-blockand bleed valves or double-block and blind valves.

In an embodiment, the feed header 552 is provided to allow a hydrocarbonfeed stream flowing through line 551 to be directed to any furnacepreceding an adiabatic reactor, and an adiabatic reactor effluent may beremoved downstream of any one of the adiabatic reactors. A series ofvalves may be provided in the lines between the feed header 552 and theinlet to any one of the furnaces 557, and 558. An intermediate productheader 569 is provided to allow the adiabatic reactor effluent from anydesired adiabatic reactor to be directed to any of the isothermalreactors; to any one of the furnaces preceding an isothermal reactor; orto a tank 579 for storage of the adiabatic reactor effluent. A series ofvalves may be provided in the lines between the intermediate productheader 569 and an inlet to any one of the furnace 574, furnace 575, andtank 579. An effluent header 588 is provided to allow the isothermalreactor effluent from any desired isothermal reactor to be directed toline 589 leading out of the reactor system. A series of valves may beprovided in the lines between the effluent header 588 and the outletline from each isothermal reactor 580, and 581. The valves may beselectively operated in a dynamic fashion to provide a desired flowscheme using a provided reactor system. As part of the dynamic flowscheme, one or more reactors in the provided reactor system may beisolated to allow the catalyst within the isolated reactors to berestored prior to being placed back into the reactor system. Additionalequipment as known in the art may also be included in the naphthareforming process. For example, a halide removal system may be includedto capture any halides evolving from the catalyst during the naphthareforming process. Additional valves, purge lines, drain lines are allwithin the processes described herein.

In an embodiment, a naphtha reforming process 550 may be carried outusing the reactor configuration shown in FIG. 5B. At the inlet of theprocess, a hydrocarbon feed stream may first pass through line 551, andinitially enter the reactor system via the feed header 552. A firsthydrocarbon feed stream passing from the feed header 552 via open valve553 through line 555 can be heated in a first furnace 557 to increasethe temperature of the hydrocarbon feed stream. The heated firsthydrocarbon feed stream passing through line 559 can be introduced to afirst adiabatic reactor 561, where the first adiabatic reactor 561 canbe an adiabatic radial flow reactor comprising a first catalyst bed 563disposed therein, and where the first catalyst bed 563 can comprise afirst naphtha reforming catalyst. At least a portion of the convertiblehydrocarbons in the first hydrocarbon feed stream can be converted toaromatic hydrocarbons in the first adiabatic reactor 561 to form a firstadiabatic reactor effluent. The first adiabatic reactor effluent passingthrough line 565 can be communicated to the intermediate product header569 via open valve 567. A second hydrocarbon feed stream passing fromthe feed header 552 via open valve 554 through line 556 can be heated ina second furnace 558 to increase the temperature of the hydrocarbon feedstream. The heated second hydrocarbon feed stream passing through line560 can be introduced to a second adiabatic reactor 562, where thesecond adiabatic reactor 562 can be an adiabatic radial flow reactorcomprising a second catalyst bed 564 disposed therein, and where thesecond catalyst bed 564 can comprise a first naphtha reforming catalyst.At least a portion of the convertible hydrocarbons in the secondhydrocarbon feed stream can be converted to aromatic hydrocarbons in thesecond adiabatic reactor 562 to form a second adiabatic reactoreffluent. The second adiabatic reactor effluent passing through line 566can be communicated to the intermediate product header 569 via openvalve 568.

In some embodiments of FIG. 5B, the first adiabatic reactor 561 can beisolated by closed valves 553 and 567, for example for servicing (e.g.,restoring naphtha reforming catalyst activity) the first adiabaticreactor 561, while allowing the naphtha reforming process to continue tooperate via the second adiabatic reactor 562. Once the servicing of thefirst adiabatic reactor 561 is completed, the first adiabatic reactor561 can be reintroduced to the naphtha reforming process by openingvalves 553 and 567. In other embodiments of FIG. 5B, the secondadiabatic reactor 562 can be isolated by closed valves 554 and 568, forexample for servicing (e.g., restoring naphtha reforming catalystactivity) the second adiabatic reactor 562, while allowing the naphthareforming process to continue to operate via the first adiabatic reactor561. Once the servicing of the second adiabatic reactor 562 iscompleted, the second adiabatic reactor 562 can be reintroduced to thenaphtha reforming process by opening valves 554 and 568.

An adiabatic reactor effluent (e.g., first adiabatic reactor effluentand/or second adiabatic reactor effluent) passing from the intermediateproduct header 569 via open valve 570 through line 572 can be heated ina third furnace 574 to increase the temperature of the adiabatic reactoreffluent. The heated adiabatic reactor effluent passing through line 576can be introduced to the first isothermal reactor 580, where the firstisothermal reactor 580 can operate under isothermal naphtha reformingconditions. The first isothermal reactor 580 can comprise a plurality oftubes 582 having a second naphtha reforming catalyst disposed therein,where the plurality of tubes 582 can be disposed within a first reactorfurnace 590. The first naphtha reforming catalyst and the second naphthareforming catalyst can be the same or different. At least an additionalportion of the convertible hydrocarbons in the adiabatic reactoreffluent can be converted to aromatic hydrocarbons in the firstisothermal reactor 580 to form a first isothermal reactor effluentpassing through line 584. The first isothermal reactor effluent passingthrough line 584 can be communicated to the effluent header 588 via openvalve 586. The adiabatic reactor effluent passing from the intermediateproduct header 569 via open valve 571 through line 573 can be heated ina fourth furnace 575 to increase the temperature of the adiabaticreactor effluent. The heated adiabatic reactor effluent passing throughline 577 can be introduced to the second isothermal reactor 581, wherethe second isothermal reactor 581 can operate under isothermal naphthareforming conditions. The second isothermal reactor 581 can comprise aplurality of tubes 583 having a second naphtha reforming catalystdisposed therein, where the plurality of tubes 583 can be disposedwithin a second reactor furnace 591. At least an additional portion ofthe convertible hydrocarbons in the adiabatic reactor effluent can beconverted to aromatic hydrocarbons in the second isothermal reactor 581to form a second isothermal reactor effluent passing through line 585.The second isothermal reactor effluent passing through line 585 can becommunicated to the effluent header 588 via open valve 587. Anisothermal reactor effluent (e.g., first isothermal reactor effluentand/or second isothermal reactor effluent) can be communicated from theeffluent header 588 to line 589 leading out of the reactor system.

In some embodiments of FIG. 5B, the first isothermal reactor 580 can beisolated by closed valves 570 and 586, for example for servicing (e.g.,restoring naphtha reforming catalyst activity) the first isothermalreactor 580, while allowing the naphtha reforming process to continue tooperate via the second isothermal reactor 581. Once the servicing of thefirst isothermal reactor 580 is completed, the first isothermal reactor580 can be reintroduced to the naphtha reforming process by openingvalves 570 and 586. In other embodiments of FIG. 5B, the secondisothermal reactor 581 can be isolated by closed valves 571 and 587, forexample for servicing (e.g., restoring naphtha reforming catalystactivity) the second isothermal reactor 581, while allowing the naphthareforming process to continue to operate via the first isothermalreactor 580. Once the servicing of the second isothermal reactor 581 iscompleted, the second isothermal reactor 581 can be reintroduced to thenaphtha reforming process by opening valves 571 and 587.

In an embodiment, during the operation of the reactor system forcarrying out a naphtha reforming process as disclosed herein at leastone reactor (e.g., an adiabatic reactor, an isothermal reactor, etc.)may be deemed to have an operational issue. In an embodiment, the natureof the operational issue may comprise a decrease in catalytic activityor selectivity over time. A catalyst (e.g., naphtha reforming catalyst)that exhibits an unacceptably low catalytic performance compared to aninitial catalytic performance can be described as a “spent” catalyst(e.g., spent reforming catalyst or spent naphtha reforming catalyst). Inan embodiment, the nature of the operational issue may compriseinspection and/or servicing of the reactor containing the catalyst. Inanother embodiment, the nature of the operational issue may compriseinspection and/or servicing of the safety systems associated with thereactor containing the catalyst. In an embodiment, the operational issuemay be based on operational considerations, economic considerations,catalyst performance, or any combination thereof.

In an embodiment, the catalyst (e.g., naphtha reforming catalyst) usedin the naphtha reforming process may experience a decrease in catalyticactivity or selectivity over time. The resulting deactivation of thecatalyst can result from a number of mechanisms including, but notlimited to, coking, poisoning, and/or loss of catalytic material orcomponents. As used herein, the term “coke” refers to a carbon-richcarbonaceous material, generally having a C/H mole ratio >1. The term“coking” refers to the process of depositing coke on a surface. Both theterm “coke” and “coking” as used herein are meant to include theconventional meaning known in the art. In an embodiment, a catalyst canbe deemed a spent catalyst when the catalytic activity is less than orequal to about 50%, alternatively about 40%, alternatively about 30%,alternatively 20%, or alternatively 10% of the initial catalyticactivity of the catalyst when initially placed into service. In anembodiment, a catalyst can be deemed a spent catalyst when the catalyticselectivity as measured by the production of hydrocarbons with fivecarbon atoms or less (C₅—) is more than or equal to about 150% of thecatalyst when initially placed into service. In an embodiment, acatalyst may be deemed to be a spent catalyst based on catalystperformance, alone or in combination with operational considerations,and/or economic considerations. For example, the catalyst may be deemedto be spent when the income attributable to an improved conversionefficiency, and thus an increased product yield, as a result ofreplacing the catalyst outweighs the expense of replacing the catalyst.

Molar selectivities are defined as:

$\begin{matrix}{{{Benzene}\mspace{14mu}{selectivity}\text{:}\mspace{14mu} S_{Bz}} = \frac{{\overset{.}{n}}_{{Bz},{prod}}}{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{feed}} - {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{prod}}}} & {{Eq}.\mspace{14mu} 1} \\{{{Toluene}\mspace{14mu}{selectivity}\text{:}\mspace{14mu} S_{Tol}} = \frac{{\overset{.}{n}}_{{Tol},{prod}}}{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 7},{feed}} - {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 7},{prod}}}} & {{Eq}.\mspace{14mu} 2} \\{{{Benzene} + {{Toluene}\mspace{14mu}{selectivity}\text{:}\mspace{14mu} S_{{Bz} + {Tol}}}} = \;\frac{{\overset{.}{n}}_{{Bz},{prod}} + {\overset{.}{n}}_{{Tol},{prod}}}{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{C\; 7},{feed}} - {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{C\; 7},{prod}}}} & {{Eq}.\mspace{14mu} 3} \\{{{Aromatics}\mspace{14mu}{selectivity}\text{:}\mspace{14mu} S_{arom}} = \frac{{\overset{.}{n}}_{{Bz},{prod}} + {\overset{.}{n}}_{{Tol},{prod}} + {\overset{.}{n}}_{{{C\; 8} + {arom}},{prod}}}{{\overset{.}{n}}_{{{{conv}\mspace{14mu} C\; 6} - {C\; 8} +},{feed}} - {\overset{.}{n}}_{{{{conv}\mspace{14mu} C\; 6} - {C\; 8} +},{prod}}}} & {{Eq}.\mspace{14mu} 4}\end{matrix}$

Conversion is defined as the number of moles converted per mole of“convertible” hydrocarbons fed:

$\begin{matrix}{{C_{6}\mspace{14mu}{conversion}\text{:}\mspace{14mu} X_{C\; 6}} = \frac{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{feed}} - {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{prod}}}{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{feed}}}} & {{Eq}.\mspace{14mu} 5} \\{{C_{7}\mspace{14mu}{conversion}\text{:}\mspace{14mu} X_{C\; 7}} = \frac{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 7},{feed}} - {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 7},{prod}}}{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 7},{feed}}}} & {{Eq}.\mspace{14mu} 6} \\{{C_{6} + {C_{7}\mspace{14mu}{conversion}\text{:}\mspace{14mu} X_{{C\; 6} + {C\; 7}}}} = \frac{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{feed}} + {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 7},{feed}} - {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{prod}} - {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 7},{prod}}}{{\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 6},{feed}} + {\overset{.}{n}}_{{{conv}\mspace{14mu} C\; 7},{feed}}}} & {{Eq}.\mspace{14mu} 7}\end{matrix}$

In these equations (equations 1 through 7), {dot over (n)} indicates amolar flow rate in a continuous reactor or the number of moles in abatch reactor.

The ability of a reactor containing the spent catalyst (e.g., adiabaticreactor, isothermal reactor, etc.) to convert convertible hydrocarbons(e.g., aliphatic, alicyclic, and/or naphthenic hydrocarbons) in thehydrocarbon feed stream to aromatic hydrocarbons can be restored. In anembodiment, the ability to convert aliphatic, alicyclic, and/ornaphthenic hydrocarbons to aromatic hydrocarbons can be restored byreplacing the spent catalyst in the reactor with fresh catalyst, and/orrejuvenating the catalyst. Catalyst rejuvenation is described in moredetail below. Suitable procedures known in the art may be used toreplace the spent catalyst in the reactor with fresh catalyst at desiredintervals. In an embodiment, each reactor may be restored at an equaltime interval based on the expected life of the catalyst in the naphthareforming process. In an embodiment, each reactor may be restored basedon measurable indicators of the catalyst activity. For example, anoutlet temperature rise may indicate a loss of activity for anendothermic reaction, and/or a decrease in the product concentration atthe outlet of the reactor may indicate a decrease in the catalystactivity or performance. The fresh catalyst has a higher activity orperformance as compared to the spent catalyst. The spent catalyst maythen be disposed of or recycled to recover active catalytic materialsfor future use.

In an embodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can comprise a catalyst rejuvenation systemcoupled to the plurality of adiabatic reactors by a plurality of flowlines. The reactor system can further comprise a plurality of valvesdisposed in the one or more feed lines, the one or more product lines,and the flow lines, where the plurality of valves are configured to bedynamically operated to isolate at least one of the adiabatic reactorsof the plurality of adiabatic reactors and fluidly couple the at leastone isolated adiabatic reactor to the catalyst rejuvenation system whilethe remaining adiabatic reactors remain operational. The at least oneisolated adiabatic reactor can comprise a spent naphtha reformingcatalyst, and the catalytic activity in the isolated reactor(s) can berestored.

In an embodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can comprise a catalyst rejuvenation systemcoupled to one or more isothermal reactors by a plurality of flow lines.The reactor system can further comprise a plurality of valves disposedin the one or more inlet lines, the one or more effluent lines, and theflow lines, where the plurality of valves are configured to bedynamically operated to isolate at least one isothermal reactor of theone or more isothermal reactors and fluidly couple the at least oneisolated isothermal reactor to the catalyst rejuvenation system whilethe remaining isothermal reactors remain operational. The at least oneisolated isothermal reactor can comprise a spent naphtha reformingcatalyst, and the catalytic activity in the isolated reactor(s) has tobe restored.

In an embodiment, preparing the reactor (e.g., adiabatic reactor,isothermal rector) to resume conversion of the hydrocarbon feed streamcomprising the convertible hydrocarbons (e.g., aliphatic, alicyclic,and/or naphthenic hydrocarbons) can comprise reducing the catalyst witha compound that reversibly reduces the activity of the catalyst (e.g.poisons the catalyst). Suitable compounds may include, but are notlimited to, hydrogen, halides, carbon monoxide, or organic moleculesthat may reversibly adsorb and later desorb from the catalyst. Byreversibly reducing the reactivity of the catalyst (e.g. poisoning thecatalyst), the conversion in the restored reactor may be more graduallyincreased when hydrocarbons are reintroduced to the reactor.

Catalyst rejuvenation generally refers to restoring the catalyst byremoving one or more contaminants on the catalyst. For example,rejuvenation may involve the conversion of carbonaceous material on thecatalyst to carbon oxides and water. Decoking is one example of arejuvenation process. In this process, oxygen, which may be supplied inthe form of air, either air or air diluted with nitrogen, is provided tothe reactor (e.g., an isolated reactor for in situ rejuvenation) at anappropriate temperature. The carbon deposits are thereby oxidized toform carbon dioxide and water. The rejuvenation process may continueuntil a desired level of rejuvenation has occurred.

In an embodiment, a catalyst rejuvenation process may be carried out byheating the spent catalyst to a temperature ranging of from about 25° C.to about 1,000° C., alternatively from about 50° C. to about 900° C.,alternatively from about 100° C. to about 800° C., alternatively from200° C. to 700° C., or alternatively from 300° C. to 600° C. to producea decoked spent catalyst. The decoking process may be carried out byheating the spent catalyst for a time of from about 1 hour to about 40hours, alternatively from about 2 hours to about 25 hours, alternativelyfrom about 3 hours to about 20 hours, alternatively from 4 hours to 15hours, or alternatively from 5 hours to 10 hours to produce a decokedspent catalyst. As discussed above, the decoking process may be carriedout by heating the spent catalyst in the presence of oxygen, and theoxygen concentration may be from about 0.01 mol % to about 20 mol %,alternatively from about 0.1 mol % to about 15 mol %, alternatively fromabout 0.2 mol % to about 10 mol %, alternatively from about 0.5 mol % toabout 5 mol %, or alternatively from about 1 mol % to about 3 mol % toproduce a decoked spent catalyst. Suitable rejuvenation processes thatcan be used in accordance with the present disclosure are disclosed inU.S. Pat. Nos. 4,937,215; 5,260,238; 5,155,075; 4,851,380; and7,868,217; each of which is incorporated by reference herein in itsentirety.

In an embodiment, a catalyst rejuvenation system can be used torejuvenate the catalyst in an isolated reactor. As used herein,rejuvenation refers to a process of reactivating a spent catalyst bydecreasing coke content, redispersing metals, and/or introducing areplacement and/or additional catalytic component to the catalyst inorder to increase the activity of the catalyst. In an embodiment,rejuvenating a catalyst comprises redispersing the metal in the spentcatalyst to produce a redispersed spent catalyst, contacting theredispersed spent catalyst with a reactivating composition to produce aredispersed, reactivated spent catalyst, and thermally treating theredispersed, reactivated spent catalyst to produce a reactivatedcatalyst.

In an embodiment, rejuvenating the spent catalyst may begin by decokingthe catalyst. Any of the decoking processes described above with respectto the rejuvenation of the spent catalyst may be used to decoke thecatalyst. Following decoking of the spent catalyst, the metal on thedecoked spent catalyst may be redispersed on the catalyst support.Without wishing to be limited by theory, the decoking process incombination with the hydrocarbon conversion process that the spentcatalyst was subjected to, may have led to the agglomeration of themetal on the catalyst support. The agglomerated metal may not be fullyavailable physically and chemically to the catalytic reactions and thusmay be redispersed to increase the catalyst activity.

In an embodiment, the metal on the decoked spent catalyst is redispersedusing one or more processes generally referred to as oxychlorination.Oxychlorination of the decoked spent catalyst may be carried out bycontacting the decoked spent catalyst with a redispersing composition.Suitable redispersing compositions may comprise a chlorine-containingcompound and oxygen. The chlorine-containing compound may be in a solidphase, liquid phase, gas phase, or any combination thereof. Examples ofchlorine-containing compounds suitable for use in the redispersingcomposition include without limitation hydrochloric acid, chlorine,carbon tetrachloride, tetrachloroethylene, chlorobenzene, methylchloride, methylene chloride, chloroform, allyl chloride,trichloroethylene, chloramine, chlorine oxides, chlorine acids, chlorinedioxide, dichlorine monoxide, dichlorine heptoxide, chloric acid,perchloric acid, or any combination thereof.

Contacting of the decoked spent catalyst with the redispersingcomposition may be carried out over a time period of from about 0.5hours to about 50 hours, alternatively from about 1 hour to about 20hours, alternatively from about 2 hours to about 10 hours, at atemperature in the range of from about 25° C. to about 1,000° C.,alternatively from about 50° C. to about 900° C., alternatively fromabout 100° C. to about 800° C., alternatively from about 200° C. toabout 400° C., or alternatively from about 400° C. to about 600° C.Contacting of the decoked spent catalyst with the redispersingcomposition may be carried out in the presence of oxygen. When oxygen isused, the oxygen concentration may range from about 0.01 mol % to about20 mol %, alternatively from about 1 mol % to about 18 mol %,alternatively from about 5 mol % to about 15 mol %, or alternativelyfrom about 8 mol % to about 12 mol %.

In an embodiment, the decoked spent catalyst is contacted with aredispersing composition comprising a chlorine-containing compound(e.g., HCl) and oxygen in the presence of water. When water is used, thewater to HCl mole ratio (H₂O:HCl) may be from about 0.01:1 to about10:1, alternatively from about 0.5:1 to about 5:1, or alternatively fromabout 1:1 to about 3:1. When chlorine-containing compounds are usedother than HCl, the H₂O:HCl mole ratio is calculated based on theequivalent amount of HCl generated in the presence of the spentcatalyst.

The spent catalyst may be subjected to a reactivation step, which mayoccur after the decoked spent catalyst has undergone a redispersion asdescribed above. In an embodiment, reactivation of the decoked,redispersed spent catalyst may be carried out using a reactivatingcomposition comprising one or more halogenating agents, including gasphase halogenating agents, liquid phase halogenating agents, solid phasehalogenating agents, or any combination thereof. In an embodiment,reactivation of the decoked, redispersed spent catalyst is carried outby contacting the decoked, redispersed spent catalyst with afluorine-containing solution in a process generally referred to asfluoridation. The fluorine-containing compound may be in the solidphase, liquid phase, gas phase, or any combination thereof. Examples offluorine-containing compounds suitable for use in this disclosureinclude without limitation tetramethylammonium fluoride (TMAF), ammoniumfluoride (NH₄F or AF), tetrafluoroethylene, 2,2,2-trifluoroethanol(TFE), fluorine (F₂), hydrofluoric acid (HF), or combinations thereof.In an embodiment, the fluorine-containing compound is a perfluorinatedalkane, perfluorinated alcohol, or mixtures thereof. Examples ofperfluorinated alcohols suitable for use in this disclosure includewithout limitation 2,2,2-trifluoroethanol (TFE), hexafluoroisopropanol,tetrafluoropropanol, pentafluoropropanol, hexafluorophenylpropanol,perfluorobutyl alcohol, hexafluor-2-propanol, pentafluoro-1-propanol,tetrafluoro-1-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol,2,2,3,3,3-pentafluoro-1-propanol, and any combination thereof.

In an embodiment, the fluorine-containing compound is an ammonium halidecompound and may comprise one or more compounds represented by thegeneral formula N(R)₄F, where R represents a hydrogen or a substitutedor unsubstituted carbon chain molecule having from 1 to 20 carbons,where each R may be the same or different. In an embodiment, R ismethyl, ethyl, propyl, butyl, or combinations thereof. Alternatively, Ris methyl. Examples of suitable ammonium compounds include ammoniumfluoride (AF), tetramethylammonium fluoride (TMAF), tetraethylammoniumfluoride (TEAF), tetrapropylammonium fluoride, tetrabutylammoniumfluoride, methyltriethylammonium fluoride, or any combination thereof.Alternatively, the ammonium halide compound may also comprise at leastone hydrofluoric acid and at least one ammonium hydroxide represented bythe formula N(R′)₄OH, where R′ is hydrogen or a substituted orunsubstituted carbon chain molecule having from 1 to 20 carbon atoms,where each R′ may be the same or different. In an embodiment, R′ ismethyl, ethyl, propyl, butyl, or combinations thereof. Alternatively, R′is methyl. Examples of ammonium hydroxides suitable for use in thisdisclosure include ammonium hydroxide, tetraalkylammonium hydroxidessuch as tetramethylammonium hydroxide, tetraethylammonium hydroxide,tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, or anycombination thereof.

In an embodiment the decoked, redispersed spent catalyst is contactedwith a solution of TMAF in the temperature range of from about 0° C. toabout 200° C., alternatively from about 20° C. to about 100° C., oralternatively from about 40° C. to about 60° C. for a time period offrom about 1 minute to about 100 hours, alternatively from about 0.1hours to about 50 hours, or alternatively from about 1 hour to about 24hours. The solution of TMAF may also contain one or more suitablesolvents.

In an embodiment, the decoked, redispersed spent catalyst may bereactivated through contact with a gas phase fluoridating agent such as,for example, fluorine. In such an embodiment, the gas phase fluoridatingagent may be contacted with a decoked, redispersed spent catalyst for atime period of from about 1 minute to about 100 hours, alternativelyfrom about 0.1 hours to about 50 hours, alternatively from about 1 hourto about 24 hours, or alternatively from about 4 hours to about 11hours.

A chlorine-containing compound may also be utilized in the reactivationof the decoked, redispersed spent catalyst. The chlorine-containingcompound may be in the solid phase, liquid phase, gas phase, or anycombination thereof. In an embodiment, the chlorine-containing compoundis of the type described above. Examples of chlorine-containingcompounds suitable for use in the reactivating composition includewithout limitation compounds represented by the general formulaN(R″)₄Cl, where R″ represents a hydrogen or a substituted orunsubstituted carbon chain molecule having 1 to 20 carbons where each R″may be the same or different. In an embodiment, R″ is methyl, ethyl,propyl, butyl, or combinations thereof. Alternatively, R″ is methyl.Specific examples of suitable organic ammonium chlorine compoundsinclude ammonium chloride, tetramethylammonium chloride (TMAC),tetraethylammonium chloride, tetrapropylammonium chloride,tetrabutylammonium chloride, methyltriethylammonium chloride, orcombinations thereof. Alternatively, the chlorine-containing compound isTMAC.

In some aspects, a method of rejuvenating the naphtha reforming catalystcan comprise (1) contacting a spent catalyst with a chlorine-containingstream comprising a chlorine-containing compound to produce achlorinated spent catalyst (e.g., chlorination); (2) contacting thechlorinated spent catalyst with a decoking gas stream comprising oxygento produce a de-coked catalyst; and (3) contacting the de-coked catalystwith a fluorine-containing stream comprising a fluorine-containingcompound (e.g., fluorination) to produce a rejuvenated naphtha reformingcatalyst.

Referring now to step (1) of the method of rejuvenating the naphthareforming catalyst, the chlorine-containing compound in thechlorine-containing stream may be any suitable chlorine-containingcompound or any chlorine-containing compound disclosed herein. Forinstance, illustrative chlorine-containing compounds may include, butare not limited to, hydrochloric acid, chlorine gas (Cl₂), carbontetrachloride, tetrachloroethylene, chlorobenzene, methyl chloride,methylene chloride, chloroform, allyl chloride, trichloroethylene, achloramine, a chlorine oxide, a chlorine acid, chlorine dioxide,dichlorine monoxide, dichlorine heptoxide, chloric acid, perchloricacid, ammonium chloride, tetramethylammonium chloride,tetraethylammonium chloride, tetrapropylammonium chloride,tetrabutylammonium chloride, methyltriethylammonium chloride, and thelike, or any combination thereof. Other suitable chlorine-containingcompounds may include arenes and alkyl-substituted arenes (e.g.,benzene, toluene, and xylenes) where at least one hydrogen atom isreplaced with a Cl atom.

In some aspects, the chlorine-containing compound may comprise (orconsist essentially of, or consist of) hydrochloric acid; alternatively,chlorine gas (Cl₂); alternatively, carbon tetrachloride; alternatively,tetrachloroethylene; alternatively, chlorobenzene; alternatively, methylchloride; alternatively, methylene chloride; alternatively, chloroform;alternatively, allyl chloride; alternatively, trichloroethylene;alternatively, a chloramine; alternatively, a chlorine oxide;alternatively, a chlorine acid; alternatively, chlorine dioxide;alternatively, dichlorine monoxide; alternatively, dichlorine heptoxide;alternatively, chloric acid; alternatively, perchloric acid;alternatively, ammonium chloride; alternatively, tetramethylammoniumchloride; alternatively, tetraethylammonium chloride; alternatively,tetrapropylammonium chloride; alternatively, tetrabutylammoniumchloride; or alternatively, methyltriethylammonium chloride.

In other aspects, the chlorine-containing compound may comprise (orconsist essentially of, or consist of) chlorine gas (Cl₂). In additionto the chlorine-containing compound, the chlorine-containing stream mayfurther comprise an inert gas, such as helium, neon, argon, nitrogen, orcombinations of two or more of these materials. In certain aspects, thechlorine-containing stream may comprise (or consist essentially of, orconsist of) a chlorine-containing compound and an inert gas, and theinert gas may be or may comprise nitrogen. In a further aspect, thechlorine-containing stream may comprise (or consist essentially of, orconsist of) chlorine gas (Cl₂) and nitrogen.

While not being limited thereto, the amount of chlorine (Cl) in thechlorine-containing stream often may be less than about 15% by volume.For instance, the chlorine-containing stream may comprise an amount ofthe chlorine-containing compound that is controlled to give aconcentration in ppmv (ppm by volume) of Cl in the chlorine-containingstream of less than about 100,000; alternatively, a ppmv of Cl of lessthan about 50,000; alternatively, a ppmv of Cl of less than about25,000; alternatively, a ppmv of Cl of less than about 10,000. Suitableranges for the concentration of Cl may include, but are not limited to,the following ranges: from about 50 to about 100,000 ppmv, from about 50to about 50,000 ppmv, from about 50 to about 25,000 ppmv, from about 100to about 20,000 ppmv, from about 250 to about 25,000 ppmv, from about500 to about 25,000 ppmv, from about 1,000 to about 25,000 ppmv, fromabout 5,000 to about 50,000 ppmv, from about 2,500 to about 35,000 ppmv,or from about 7,500 to about 35,000 ppmv, and the like.

The chlorine-containing stream may be substantially free of anoxygen-containing compound (e.g., oxygen (O₂) and water (H₂O)), i.e.,may contain less than 100 ppmw (ppm by weight) of an oxygen-containingcompound. Therefore, it is contemplated that the amount of anyoxygen-containing compound in the chlorine-containing stream may be lessthan 50 ppmw, less than 25 ppmw, less than 10 ppmw, less than 5 ppmw, orless than 3 ppmw, in certain aspects. In other aspects, the amount ofany oxygen-containing compound in the chlorine-containing stream may bein range from about 0.1 to 100 ppmw, from about 0.5 to 100 ppmw, fromabout 1 to 100 ppmw, from about 0.1 to about 50 ppmw, from about 0.1 toabout 25 ppmw, from about 0.1 to about 10 ppmw, or from about 0.1 toabout 5 ppmw. While not wishing to be bound by theory, it is believedthat it may be beneficial to have substantially no oxygen added duringthe chlorination step of the method of rejuvenating a spent catalyst.Moreover, although not required, the chlorine-containing stream may besubstantially free of fluorine-containing compounds, i.e., may containless than 100 ppmw (ppm by weight) of fluorine-containing compounds. Asabove, it is contemplated that the amount of fluorine-containingcompounds in the chlorine-containing stream may be, for instance, lessthan 50 ppmw, less than 10 ppmw, in a range from about 0.1 to 100 ppmw,in a range from about 0.1 to about 50 ppmw, or in a range from about 0.1to about 10 ppmw, and the like.

The chlorination step (1) may be conducted at a variety of temperaturesand time periods. For instance, the chlorination step may be conductedat a chlorination temperature in a range from about 0° C. to about 500°C.; alternatively, from about 0° C. to about 300° C.; alternatively,from about 20° C. to about 400° C.; alternatively, from about 20° C. toabout 300° C.; alternatively, from about 30° C. to about 300° C.;alternatively, from about 40° C. to about 300° C.; alternatively, fromabout 100° C. to about 250° C.; alternatively, from about 150° C. toabout 300° C.; alternatively, from about 200° C. to about 300° C.;alternatively, or alternatively, from about 150° C. to about 275° C. Inthese and other aspects, these temperature ranges also are meant toencompass circumstances where the chlorination step is conducted at aseries of different temperatures, instead of at a single fixedtemperature, falling within the respective ranges.

The duration of the chlorination step is not limited to any particularperiod of time. Hence, the chlorination step may be conducted, forexample, in a time period ranging from as little as 30-45 minutes to aslong as 12-24 hours, 36-48 hours, or more. The appropriate chlorinationtime may depend upon, for example, the chlorination temperature and theamount of chlorine in the chlorine-containing stream, among othervariables. Generally, however, the chlorination step may be conducted ina time period that may be in a range from about 45 minutes to about 48hours, such as, for example, from about 1 hour to about 48 hours, fromabout 45 minutes to about 24 hours, from about 45 minutes to about 18hours, from about 1 hour to about 12 hours, from about 2 hours to about12 hours, from about 4 hours to about 10 hours, or from about 2 hours toabout 8 hours.

Step (2) of the method of rejuvenating the naphtha reforming catalystoften may be referred to as the carbon burn step, or decoking step, andin this step, a chlorinated spent catalyst may be contacted with adecoking gas stream comprising oxygen. In addition to oxygen, thedecoking gas stream may comprise an inert gas, i.e., the decoking gasstream may comprise (or consist essentially of, or consist of) oxygenand an inert gas. Typical inert gasses useful in the carbon burn stepmay encompass helium, neon, argon, nitrogen, and the like, and thisincludes combinations of two or more of these materials. In certainaspects, the decoking gas stream may comprise (or consist essentiallyof, or consist of) oxygen and nitrogen; alternatively, air and nitrogen;or alternatively, air.

Since the decoking gas stream may comprise air, the decoking gas streammay comprise about 20-21 mole % oxygen. More often, however, the amountof oxygen in the decoking gas stream may be less than about 10 mole %.For example, in some aspects, the decoking gas stream may comprise lessthan about 8 mole %, less than about 5 mole %, or less than about 3 mole% oxygen. Accordingly, suitable ranges for the mole % of oxygen in thedecoking gas stream may include, but are not limited to, the followingranges: from about 0.1 to about 25 mole %, from about 0.1 to about 20mole %, from about 0.1 to about 10 mole %, from about 0.2 to about 10mole %, from about 0.2 to about 5 mole %, from about 0.3 to about 5 mole%, from about 0.5 to about 5 mole %, from about 0.5 to about 4 mole %,from about 0.5 to about 3 mole %, or from about 1 to about 3 mole %, andthe like.

In an aspect, the decoking gas stream may be substantially halogen-free,i.e., substantially free of halogen-containing compounds. In thiscontext, “substantially halogen-free” means less than 100 ppmw (ppm byweight) of halogen-containing compounds, such as chlorine-containingcompounds, in the decoking gas stream. Therefore, it is contemplatedthat the amount of halogen-containing compounds in the decoking gasstream may be less than 50 ppmw, less than 40 ppmw, less than 25 ppmw,less than 10 ppmw, less than 5 ppmw, or less than 3 ppmw, in certainaspects. In other aspects, the amount of halogen-containing compounds inthe decoking gas stream may be in range from about 0.1 to 100 ppmw, fromabout 0.5 to 100 ppmw, from about 1 to 100 ppmw, from about 0.1 to about50 ppmw, from about 0.1 to about 25 ppmw, from about 0.1 to about 10ppmw, or from about 0.1 to about 5 ppmw. While not wishing to be boundby theory, it is believed that it may be beneficial to havesubstantially no halogens, such as chlorine, added during the carbonburn step of the method of rejuvenating a spent catalyst.

In another aspect, the decoking gas stream may be substantially free ofwater, and in this regard, “substantially free” means less than 100 ppmw(ppm by weight) of water in the decoking gas stream. Therefore, it iscontemplated that the amount of water in the decoking gas stream may beless than 50 ppmw, less than 25 ppmw, less than 10 ppmw, less than 5ppmw, or less than 3 ppmw, in certain aspects. In other aspects, theamount of water in the decoking gas stream may be in range from about0.1 to 100 ppmw, from about 0.5 to 100 ppmw, from about 1 to 100 ppmw,from about 0.1 to about 50 ppmw, from about 0.1 to about 25 ppmw, fromabout 0.1 to about 10 ppmw, or from about 0.1 to about 5 ppmw. While notwishing to be bound by theory, it is believed that it may be beneficialto have substantially no water added during the carbon burn step of themethod of rejuvenating a spent catalyst.

Similar to that described above for the chlorine-containing stream, anycompositional attributes of the decoking gas stream are meant to referto the incoming decoking gas stream, prior to contacting the chlorinatedspent catalyst and the metal reactor, unless expressly stated otherwise.As one of skill in the art would readily recognize, the outgoingdecoking gas stream, after contacting the chlorinated spent catalyst,may vary significantly in composition from the incoming decoking gasstream. For instance, chlorine deposited during the chlorination mayelute, in some circumstances, from the catalyst during the carbon burnstep. Moreover, water may be produced during the carbon burn step, andthus, water may be detected in the outgoing decoking gas stream.

The carbon burn step may be conducted at a variety of temperatures andtime periods. For instance, the carbon burn step may be conducted at apeak decoking temperature in a range from about 150° C. to about 600°C.; alternatively, from about 200° C. to about 500° C.; alternatively,from about 300° C. to about 600° C.; alternatively, from about 300° C.to about 550° C.; alternatively, from about 300° C. to about 500° C.;alternatively, from about 320° C. to about 480° C.; alternatively, fromabout 340° C. to about 460° C.; or alternatively, from about 350° C. toabout 450° C. In these and other aspects, these temperature ranges alsoare meant to encompass circumstances where the carbon burn step isconducted at a series of different temperatures (e.g., an initialdecoking temperature, a peak decoking temperature), instead of at asingle fixed temperature, falling within the respective ranges. Forinstance, and not limited thereto, the carbon burn step may start at aninitial decoking temperature which is the same as a chlorine purgingtemperature (discussed further herein below). Thus, for example, thecarbon burn step may commence at an initial decoking temperature in arange from about 0° C. to about 300° C., from about 20° C. to about 250°C., from about 50° C. to about 200° C., or from about 150° C. to about260° C. Subsequently, the temperature of the carbon burn step may beincreased to a peak decoking temperature, for example, in a range fromabout 300° C. to about 600° C., or from about 350° C. to about 450° C.

The duration of the carbon burn step is not limited to any particularperiod of time. Hence, the carbon burn step may be conducted, forexample, in a time period ranging from as little as 30-45 minutes to aslong as 48-72 hours, or more. The appropriate decoking time may dependupon, for example, the initial decoking temperature, the peak decokingtemperature, and the amount of oxygen in the decoking gas stream, amongother variables. Generally, however, the carbon burn step may beconducted in a time period that may be in a range from about 45 minutesto about 72 hours, such as, for example, from about 1 hour to about 72hours, from about 24 hours to about 72 hours, from about 12 hours toabout 60 hours, from about 12 hours to about 48 hours, or from about 1hour to about 6 hours.

Alternatively, the carbon burn step may be conducted for a time periodsufficient to reduce the wt. % of carbon on the chlorinated spentcatalyst to less than about 1 wt. % (a de-coked catalyst). In someaspects, the carbon burn step may be conducted for a time periodsufficient to reduce the wt. % of carbon on the chlorinated spentcatalyst to less than about 0.75 wt. %, less than about 0.5 wt. %, orless than about 0.2 wt. %. In other aspects, the carbon burn step may beconducted for a time period determined by monitoring the CO₂ level inthe outgoing or exiting decoking gas stream, after contacting thecatalyst. Hence, the carbon burn step may be conducted for a time periodsufficient to reduce the amount of CO₂ in the outgoing or exitingdecoking gas stream, after contacting the catalyst, to less than about100 ppmv, for example, less than about 50 ppmv, or less than about 20ppmv.

Alternatively, the carbon burn step may be conducted for a time periodsufficient to result in a rejuvenated catalyst having an activity thatis from about 50% to about 80% of the activity of the fresh catalyst,for example, from about 50% to about 75%, or from about 55% to about75%. In this regard, the activity of the rejuvenated catalyst is basedon returning to within about 50%-80% of the fresh catalyst activity ofthe same production run of catalyst, tested on the same equipment andunder the same method and conditions.

In step (3) of the method of rejuvenating the naphtha reformingcatalyst, the de-coked catalyst may be contacted with afluorine-containing stream comprising a fluorine-containing compound.Suitable fluorine-containing compounds may include, but are not limitedto, hydrofluoric acid, fluorine gas (F₂), 2,2,2-trifluoroethanol,tetrafluoroethylene, carbon tetrafluoride, carbon trifluoride,fluoromethane, heptafluoropropane, decafluorobutane,hexafluoroisopropanol, tetrafluoropropanol, pentafluoropropanol,hexafluorophenylpropanol, perfluorobutyl alcohol, hexafluor-2-propanol,pentafluoro-1-propanol, tetrafluoro-1-propanol,1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol,ammonium fluoride, tetramethylammonium fluoride, tetraethylammoniumfluoride, tetrapropylammonium fluoride, tetrabutylammonium fluoride,methyltriethylammonium fluoride, and the like, or any combinationthereof. Other suitable fluorine-containing compounds may include arenesand alkyl-substituted arenes (e.g., benzene, toluene, and xylenes) whereat least one hydrogen atom is replaced with a F atom.

In another aspect, the fluorine-containing compound may comprise (orconsist essentially of, or consist of) hydrofluoric acid; alternatively,fluorine gas (F₂); alternatively, 2,2,2-trifluoroethanol; alternatively,tetrafluoroethylene; alternatively, carbon tetrafluoride; alternatively,carbon trifluoride; alternatively, fluoromethane; alternatively,heptafluoropropane; alternatively, decafluorobutane; alternatively,hexafluoroisopropanol; alternatively, tetrafluoropropanol;alternatively, pentafluoropropanol; alternatively,hexafluorophenylpropanol; alternatively, perfluorobutyl alcohol;alternatively, hexafluor-2-propanol; alternatively,pentafluoro-1-propanol; alternatively, tetrafluoro-1-propanol;alternatively, 1,1,1,3,3,3-hexafluoro-2-propanol; alternatively,2,2,3,3,3-pentafluoro-1-propanol; alternatively, ammonium fluoride;alternatively, tetramethylammonium fluoride; alternatively,tetraethylammonium fluoride; alternatively, tetrapropylammoniumfluoride; alternatively, tetrabutylammonium fluoride; or alternatively,methyltriethylammonium fluoride.

In another aspect, the fluorine-containing compound may comprise (orconsist essentially of, or consist of) fluorine gas (F₂). In addition tofluorine, the fluorine-containing stream may further comprise an inertgas, such as helium, neon, argon, nitrogen, or combinations of two ormore of these materials. In yet another aspect, the fluorine-containingstream may comprise (or consist essentially of, or consist of) afluorine-containing compound and an inert gas, and the inert gas may beor may comprise nitrogen. In still another aspect, thefluorine-containing stream may comprise (or consist essentially of, orconsist of) fluorine gas (F₂) and nitrogen.

While not being limited thereto, the amount of fluorine (F) in thefluorine-containing stream often may be less than about 15% by volume.For instance, the fluorine-containing stream may comprise an amount ofthe fluorine-containing compound that is controlled to give aconcentration in ppmv (ppm by volume) of F in the fluorine-containingstream of less than about 100,000; alternatively, a ppmv of F of lessthan about 50,000; alternatively, a ppmv of F of less than about 25,000;alternatively, a ppmv of F of less than about 10,000. Suitable rangesfor the concentration of F may include, but are not limited to, thefollowing ranges: from about 50 to about 150,000 ppmv, from about 50 toabout 100,000 ppmv, from about 1,000 to about 15,000 ppmv, from about 50to about 5,000 ppmv, from about 100 to about 20,000 ppmv, from about 250to about 25,000 ppmv, from about 5,000 to about 50,000 ppmv, from about1,000 to about 25,000 ppmv, from about 5,000 to about 25,000 ppmv, fromabout 2,500 to about 35,000 ppmv, or from about 7,500 to about 35,000ppmv, and the like.

The fluorine-containing stream may be substantially free ofoxygen-containing compounds (e.g., oxygen (O₂) and water (H₂O)), i.e.,may contain less than 100 ppmw (ppm by weight) of oxygen-containingcompounds. Therefore, it is contemplated that the amount ofoxygen-containing compounds in the fluorine-containing stream may beless than 50 ppmw, less than 25 ppmw, less than 10 ppmw, less than 5ppmw, or less than 3 ppmw, in certain aspects. In other aspects, theamount of oxygen-containing compounds in the fluorine-containing streammay be in range from about 0.1 to 100 ppmw, from about 0.5 to 100 ppmw,from about 1 to 100 ppmw, from about 0.1 to about 50 ppmw, from about0.1 to about 25 ppmw, from about 0.1 to about 10 ppmw, or from about 0.1to about 5 ppmw. While not wishing to be bound by theory, it is believedthat it may be beneficial to have substantially no oxygen added duringthe fluorination step of the method of rejuvenating a spent catalyst.Moreover, although not required, the fluorine-containing stream may besubstantially free of chlorine-containing compounds, i.e., may containless than 100 ppmw (ppm by weight) of chlorine-containing compounds. Asabove, it is contemplated that the amount of chlorine-containingcompounds in the fluorine-containing stream may be, for instance, lessthan 50 ppmw, less than 10 ppmw, in a range from about 0.1 to 100 ppmw,in a range from about 0.1 to about 50 ppmw, or in a range from about 0.1to about 10 ppmw, and the like.

The fluorination step may be conducted at a variety of temperatures andtime periods. For instance, the fluorination step may be conducted at afluorination temperature in a range from about 0° C. to about 500° C.;alternatively, from about 0° C. to about 300° C.; alternatively, fromabout 20° C. to about 300° C.; alternatively, from about 20° C. to about250° C.; alternatively, from about 20° C. to about 150° C.;alternatively, from about 35° C. to about 300° C.; alternatively, fromabout 35° C. to about 200° C.; alternatively, from about 50° C. to about250° C.; alternatively, from about 50° C. to about 200° C.;alternatively, from about 100° C. to about 300° C.; alternatively, fromabout 100° C. to about 250° C.; alternatively, from about 150° C. toabout 275° C.; or alternatively, from about 15° C. to about 50° C. Inthese and other aspects, these temperature ranges also are meant toencompass circumstances where the fluorination step is conducted at aseries of different temperatures, instead of at a single fixedtemperature, falling within the respective ranges.

The duration of the fluorination step is not limited to any particularperiod of time. Hence, the fluorination step may be conducted, forexample, in a time period ranging from as little as 30-45 minutes to aslong as 12-24 hours, 36-48 hours, or more. The appropriate fluorinationtime may depend upon, for example, the fluorination temperature and theamount of fluorine in the fluorine-containing stream, among othervariables. Generally, however, the fluorination step may be conducted ina time period that may be in a range from about 45 minutes to about 48hours, such as, for example, from about 1 hour to about 48 hours, fromabout 45 minutes to about 24 hours, from about 45 minutes to about 18hours, from about 1 hour to about 12 hours, from about 2 hours to about12 hours, from about 4 hours to about 10 hours, or from about 2 hours toabout 8 hours.

In various aspects contemplated herein, the method of rejuvenating thenaphtha reforming catalyst may further include one or more optionalsteps performed prior to the chlorination step and the carbon burn step.For example, a method of rejuvenating a spent catalyst may furthercomprise a partial decoking step prior to the chlorination step, and/ormay further comprise a pre-drying step prior to the chlorination step.These optional pre-chlorination steps are discussed in greater detailherein below. In one aspect, at least one of these optional steps may beperformed in a method of rejuvenating a spent catalyst, while in anotheraspect, both of these optional steps may be performed. Thepre-chlorination steps may be performed in any order, however, in aparticular aspect, the partial decoking step may be performed first,followed by the pre-drying step.

In other aspects, a method of rejuvenating the naphtha reformingcatalyst can comprise (i) contacting the spent catalyst with ahalogen-containing stream comprising chlorine and/or fluorine to producea halogenated spent catalyst; and (ii) contacting the halogenated spentcatalyst with a decoking gas stream comprising oxygen to produce arejuvenated naphtha reforming catalyst. The chlorine and fluorine instep (i) can be introduced, in any suitable order, such as together, orsequentially in any order. Methods of rejuvenating catalysts aredescribed in more detail in U.S. application Ser. No. 15/597,189 filedon 17 May 2017; U.S. Pat. Nos. 8,716,161; 8,912,108; 9,174,895; and9,421,530; and U.S. Publication No. 2014/0213839; each of which isincorporated by reference herein in its entirety.

In addition to the embodiments disclosed herein for rejuvenating thecatalyst, suitable processes for rejuvenating the catalyst are describedin U.S. Pat. Nos. RE34,250; 4,810,683; 5,776,849; 4,855,269; 4,925,819;5,106,798; and 8,664,144; each of which is incorporated by referenceherein in its entirety. U.S. Pat. No. 4,937,215, which is also herebyincorporated by reference in its entirety, also describes a process forrejuvenating deactivated Pt-zeolite catalysts by treating the catalystat about 200-525° C. with a halogen compound. Oxygen is then added tothe mixture to remove coke and, finally, the catalyst is treated with achlorofluorocarbon compound, oxygen, and nitrogen.

In still other embodiments, the catalyst rejuvenation system may be usedto reduce a fresh catalyst in situ or otherwise prepare the catalyst forthe introduction of hydrocarbons. For example, the catalyst rejuvenationsystem may be used to flush the catalyst with nitrogen prior tointroduction of hydrocarbons to the reactor when the reactor is placedback into service for performing the naphtha reforming reactions.

In an embodiment, the catalyst rejuvenation system can comprise a halidesource whereby halide can be added to the first naphtha reformingcatalyst, the second naphtha reforming catalyst, or both duringrejuvenation. The use of a halide source can lead to halide beingpresent in the rejuvenated catalyst.

In an embodiment, preparing a reactor to resume conversion of thehydrocarbon feed stream comprising the convertible hydrocarbons cancomprise reducing the catalyst with a compound that reversibly reducesthe activity of the catalyst, as previously described herein.

Once the ability of the reactor (e.g., adiabatic reactor, isothermalreactor) to convert the convertible hydrocarbons (e.g., aliphatic,alicyclic, and/or naphthenic hydrocarbons) to aromatic hydrocarbons hasbeen restored, the reactor may be optionally prepared to resumeconversion of the hydrocarbon feed stream comprising the aliphatic,alicyclic, and/or naphthenic hydrocarbons. In an embodiment, a varietyof processes may be used to prepare the catalyst for use in the naphthareforming process. For example, the reactor may be flushed with an inertgas and the catalyst reduced prior to introduction of a hydrocarbon feedstream to the reactor. In an embodiment, the catalyst may be heatedand/or exposed to a heated inert gas to allow any components of thecatalyst that may evolve or desorb to be removed prior to contacting thecatalyst with a hydrocarbon feed stream. For example, a catalystcomprising a halide may evolve some of the halide during exposure to thehydrocarbon feed stream. Preparing the catalyst by exposing the catalystto a heated gas coupled to a halide removal system may allow a portionof the halides that would otherwise evolve or desorb during the naphthareforming process to be removed prior to the reactor being placed inservice in the reactor system. As a halide may reduce the activity ofany downstream catalysts, preparing the fresh catalysts in this way mayhelp avoid reducing the activity of the catalysts contained in the otherreactors in the naphtha reforming process. Additional suitablepreparation procedures are known in the art. In an embodiment, thereactor may not be prepared for use with the process until shortlybefore the reactor is to be placed back into service in the reactorsystem.

In some embodiments, the reaction by which the naphtha reformingcatalyst became spent can be irreversible and require that the catalystbe replaced rather than rejuvenated, and the resulting costs savings andprocess simplification may outweigh the catalyst replacement costs.

Once the catalytic activity in the isolated reactor (e.g., isolatedisothermal reactor, isolated adiabatic reactor) is restored, thecorresponding valves of the plurality of valves can be dynamicallyoperated to return the isolated reactor(s) to an operational state(e.g., back into service) by restoring fluid communication between thereactor and the corresponding inlet and outlet lines.

Once the reactor (e.g., isothermal reactor, adiabatic reactor) that hasbeen restored and prepared is placed back into service, the naphthareforming reactor system can resume operations to convert at least aportion of the convertible hydrocarbons (e.g., aliphatic, alicyclic,and/or naphthenic hydrocarbons) in the hydrocarbon feed stream toaromatic hydrocarbons. A catalyst rejuvenation process can be repeatedeach time a reactor contains a catalyst that is deemed to be spent.

In an embodiment, the naphtha reforming reactors (e.g., first reactoroperating at adiabatic conditions, second reactor operating underisothermal naphtha reforming conditions, etc.) disclosed herein canincorporate one or more improvements, when compared to conventionaladiabatic reactors and/or isothermal reactors employed in naphthareforming processes. Such improvements will be described in more detaillater herein, and can be employed in any of the process flow schemesdisclosed herein (e.g., in any flow scheme described with respect toFIGS. 1-5B).

In an embodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can comprise a first reactor operating atadiabatic conditions, where the first reactor comprises a first naphthareforming catalyst; and a second reactor operating under isothermalconditions (e.g. isothermal naphtha reforming conditions), where thesecond reactor comprises a second naphtha reforming catalyst; and wherean amount of the first naphtha reforming catalyst in the first reactoris less than amount of the second naphtha reforming catalyst in thesecond reactor. In such embodiment, the bulk (e.g., majority) of thenaphtha reforming reactions can occur in the isothermal reactor. As willbe appreciated by one of skill in the art, and with the help of thisdisclosure, the isothermal reactor can be more efficient than theadiabatic reactor, as it allows for the catalyst to be utilized moreefficiently, since the temperature is maintained above a threshold, suchas a naphtha reforming reaction threshold (e.g., the activationtemperature for naphtha reforming reactions).

In an embodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can be characterized by a weight ratio ofthe catalytic material in the first naphtha reforming catalyst of theadiabatic reactor to the catalytic material in the second naphthareforming catalyst of the isothermal reactor of from about 1:2 to about1:10, alternatively from about 1:3 to about 1:9, or alternatively fromabout 1:4 to about 1:8. As will be appreciated by one of skill in theart, and with the help of this disclosure, the adiabatic reactor cancontain more reforming catalyst per the same amount of converted orreformed hydrocarbons than the isothermal reactor, as the isothermalreactor can use more of the naphtha reforming catalyst efficiently.

In an embodiment, the operating temperatures in the first reactor and/orthe second reactor do not exceed about 1,000° F. (538° C.). The firstreactor (e.g., adiabatic reactor) can be configured to convert the mostreadily convertible hydrocarbons (e.g., cyclohexane) in the reactor feedstream to aromatic hydrocarbons, and as such does not require inlettemperatures in excess of 1,000 F (538 C). Adiabatic reactors that areconfigured to perform endothermic reactions such as the naphthareforming reactions generally have the highest temperature at the inlet,and the temperature decreases across the hydrocarbon flow path throughthe adiabatic reactor between the inlet and the outlet, where an outlettemperature of an adiabatic reactor performing an endothermic reactionis lower than the inlet temperature of the same reactor. Isothermalreactors that are configured to perform endothermic reactions such asthe naphtha reforming reactions as disclosed herein can generallymaintain a catalyst temperature above the endothermic reaction thresholdtemperature that is high enough (although below 1,000 F or 538 C) toefficiently promote the naphtha reforming reactions in the isothermalreactor, and to efficiently utilize the catalyst disposed therein.

In an embodiment, the second reactor (e.g., isothermal reactor) cancomprise a plurality of tubes having the second naphtha reformingcatalyst (e.g., particles of the second naphtha reforming catalyst)disposed therein, and where the plurality of tubes can be disposedwithin a heated portion of the reactor furnace. In an embodiment, theisothermal naphtha reforming conditions in the second reactor can bemaintained by heating the plurality of tubes of the second reactorwithin the reactor. In an embodiment, the reactor can comprise a heatsource (e.g., burners, heat exchange medium, etc.) configured to heatthe interior of the reactor furnace, e.g., heat the plurality of tubesdisposed within the reactor furnace. The plurality of tubes can beheated by burners in a radiant zone of the reactor furnace, where theburners combust (e.g., burn) a fuel to heat the tubes. Alternatively,the plurality of tubes can be heated by a heat exchange medium, forexample a molten salt such as molten fluorides (e.g., LiF, NaF, KF,etc.), molten chlorides (e.g., MgCl₂), molten nitrates, or combinationsthereof.

The first reactor effluent passing from a first adiabatic reactor to asecond reactor (e.g., isothermal reactor) can be heated within thereactor furnace prior to entering the isothermal reactor, for example ina convection zone of the reactor furnace, by convective heat from theradiant zone of reactor furnace, in a heat exchanger, or the like, aspreviously described herein.

In an embodiment, from about 15% to about 35%, alternatively from about17.5% to about 27.5%, or alternatively from about 20% to about 30% ofthe conversion of the convertible hydrocarbons of the hydrocarbon feedstream to aromatic hydrocarbons can occur in the first reactor (e.g.,adiabatic reactor) to produce the first reactor effluent.

In an embodiment, the first reactor effluent recovered from the firstreactor (e.g., adiabatic reactor) can be passed through the plurality oftubes within the second reactor (e.g., isothermal reactor), where atleast an additional portion of the convertible hydrocarbon in the firstreactor effluent can be converted to an addition amount of the aromatichydrocarbons in the second reactor to form a second reactor effluent,and where the plurality of tubes can be heated within the reactorfurnace during the converting.

In an embodiment, from about 65% to about 85%, alternatively from about67.5% to about 82.5%, or alternatively from about 70% to about 80% ofthe conversion of the convertible hydrocarbons of the hydrocarbon feedstream to aromatic hydrocarbons can occur in the second reactor (e.g.,isothermal reactor) to produce the first reactor effluent.

In an embodiment, the plurality of tubes of the second reactor (e.g.,isothermal reactor) can comprise between about 250 tubes to about 5,000tubes, alternatively between about 500 tubes to about 5,000 tubes,alternatively between about 750 tubes to about 4,000 tubes, oralternatively between about 1,000 tubes to about 3,000 tubes in thereactor furnace. When a capacity larger than about 5,000 tubes isdesired for the isothermal reactor, two or more isothermal reactors inparallel could be used. As will be appreciated by one of skill in theart, and with the help of this disclosure, multiple isothermal reactorsin parallel can be used even for a capacity less than about 5,000 tubes,such as less than about 1,000 tubes for example. The plurality of tubescan be arranged in parallel with each other between an inlet of thereactor furnace and an outlet of the reactor furnace, e.g., between aninlet of the isothermal reactor and an outlet of the isothermal reactor.In some embodiments, a plurality of isothermal reactors can be arrangedin parallel with tubes disposed in each reactor.

In an embodiment, the plurality of tubes of the second reactor (e.g.,isothermal reactor) can have an internal diameter (D) between about 0.5inches (12.7 mm) and about 4 inches (101.6 mm), alternatively betweenabout 0.5 inches (12.7 mm) and about 3 inches (76.2 mm), alternativelybetween about 1 inch (25.4 mm) and about 2.5 inches (63.5 mm),alternatively between about 1.5 inches (38.1 mm) and about 2 inches(50.8 mm), or alternatively between about 2.5 inches (63.5 mm) and about3 inches (76.2 mm).

In an embodiment, the plurality of tubes of the second reactor (e.g.,isothermal reactor) can have a length (L) to internal diameter (D) ratio(i.e., L/D ratio) between about 25 and about 150, alternatively betweenabout 25 and about 100, or alternatively between about 25 and about 50.

In an embodiment, piping and equipment used throughout the naphthareforming process as disclosed herein can be constructed of suitablematerials based on the operating conditions of the equipment. In anembodiment, nickel (Ni) and/or cobalt (Co) containing alloys can be usedin the construction of a plant for carrying out the naphtha reformingprocess as disclosed herein, including the piping and/or equipment.Suitable alloys include, but are not limited to, all alloys containingat least about 8 wt. % Ni and/or Co including 300 series austeniticstainless steels (e.g., 304, 310, 316, 321, 347), Incoloy 800, Incoloy802, heat resistant casting such as HK-40, HP-50, Manaurite XTM, andnickel base alloys such as Inconel 600, 601, 617, 625, Hastelloy C andX, Haynes 214, Nimonic 115, and Udimet 700.

However, since the operating temperatures are not to exceed 1,000° F.(538° C.), the reactor internals do not necessarily need to be coatedwith a protective coating, as there is less of a chance for coking,carburization, and metal dusting. In an embodiment, the plurality oftubes of the second reactor (e.g., isothermal reactor) do not contain ametal protective layer, such as for example a metal protective layercomprising stannide.

In some embodiments, it may be desirable to coat only the metal surfacesof the piping or equipment that contact the hydrocarbons and aromaticsat temperatures above 1,000° F. (538° C.) are made of a material or arecoated with a material having a resistance to coking, carburization, andmetal dusting. In an embodiment, the surface of the piping and equipmentthat contact hydrocarbons above 1,000° F. (538° C.) can be coated by amethod comprising plating, cladding, painting, or coating the surfacesthat contact the hydrocarbon to provide improved resistance tocarburization and metal dusting followed by heating to cure the coatingin a reducing environment to form the metal protective layer. Examplesof metal surfaces of the piping or equipment that may contact thehydrocarbons and aromatics at temperatures above 1,000° F. (538° C.)include surfaces of the furnace tubes in the furnace (e.g., firstfurnace) before an adiabatic reactor (e.g., first adiabatic reactor, orfirst reactor) and surfaces of piping that carries the effluent of thefurnace (e.g., heated hydrocarbon feed stream, heated first hydrocarbonfeed stream).

In some embodiments, it may be desirable that metal surfaces of thepiping or equipment that contact the hydrocarbons and aromatics atelevated temperatures are made of a material or are coated with amaterial having a resistance to coking, carburization, and metaldusting. In an embodiment, the surface of the piping and equipment thatcontact hydrocarbons can be treated with a metal protective layer by amethod comprising plating, cladding, painting, or coating the surfacesthat contact the hydrocarbon followed by heating to cure the coating ina reducing environment to form the metal protective layer. The metalprotective layer provides improved resistance to carburization and metaldusting. Alternatively, the surfaces can be constructed of or lined witha ceramic material.

In an embodiment, the piping and equipment used throughout the naphthareforming process as disclosed herein can have a metal-containingcoating, cladding, plating, or paint applied to at least a portion(e.g., at least about 80%, alternatively at least about 95%, oralternatively about 100%) of the surface area that is to be contactedwith hydrocarbons at process temperature. After coating, themetal-coated reactor system can be preferably heated and cured in areducing environment to produce a metal protective layer comprisingintermetallic and/or metal carbide layers. A preferred metal protectivelayer for the reactor system preferably comprises a base constructionmaterial (such as a carbon steel, a chromium steel, or a stainlesssteel) having one or more adherent metallic layers attached thereto. Anexample of metallic layer includes elemental chromium. Suitable coatingsas well as application and processing techniques are described in U.S.Pat. Nos. 5,676,821; and 6,551,660, each of which is incorporated byreference herein in its entirety.

Additional materials useful for preventing coking may include alloyscomprising aluminum. For example, the alloy may comprise at least about1 wt. % Al and more preferably at least about 4 wt. % Al up to a maximumof about 10 wt. % Al. Alternatively, the alloy may be coated with adiffusion layer of Al, where Al metal is reacted with the alloy in ahigh temperature process to form a surface diffusion layer rich inaluminum. The concentration of Al in the surface diffusion layer canrange anywhere from about 5 wt. % to roughly 30 wt. % depending upon thepreparation method. Suitable alloys and materials formed using aluminumand aluminum coating are described in more detail in U.S. Pat. No.6,803,029, which is incorporated by reference herein in its entirety.

As will be appreciated by one of skill in the art, and with the help ofthis disclosure, generally, lower overall pressures, and specifically alower pressure drop across a catalyst bed can be beneficial in fixed bedreactors such as the adiabatic reactors and the isothermal reactors usedfor the naphtha reforming reactions as disclosed herein, as the naphthareforming reactions results in a large net increase in moles during thereaction. For example, one way to lower the pressure drop across acatalyst bed can be to increase a catalyst particle size, since thenaphtha reforming reactions are not diffusion limited. Further, as willbe appreciated by one of skill in the art, and with the help of thisdisclosure, doubling a catalyst particle size could lead to halving thepressure drop across the catalyst bed.

In an embodiment, a graded catalyst bed loading can be used inside atleast one tube of the plurality of tubes of the second reactor (e.g.,isothermal reactor), where a catalyst grading can be in catalystparticle size, catalyst activity (e.g., group VIII metal loading, groupIB metal loading, Pt loading, etc.), or both. As will be appreciated byone of skill in the art, and with the help of this disclosure, thesecond reactor could be operated under isothermal naphtha reformingconditions under a non-uniform catalyst loading inside the plurality oftubes of the second reactor.

In an embodiment, a pressure drop between an inlet of the plurality oftubes of the second reactor (e.g., isothermal reactor) and an outlet ofthe plurality of tubes can be less than about 20 psia (0.14 MPa),alternatively less than about 25 psia (0.17 MPa), alternatively lessthan about 30 psia (0.21 MPa), or alternatively less than about 35 psia(0.25 MPa). In other embodiments, the pressure drop measured between aninlet of the plurality of tubes of the second reactor (e.g., isothermalreactor) and an outlet of the plurality of tubes can be from about 1psia (0.007 MPa) to about 20 psia (0.1 MPa), from about 2 psia (0.01MPa) to about 15 psia (0.01 MPa), from about 3 psia (0.02 MPa) to about12 psia (0.08 MPa). By using a graded catalyst loading into theplurality of tubes of the second reactor, where the grading is based oncatalyst particle size, the pressure drop across the second reactor canbe lowered, which can in turn allow for a lower inlet pressure for theinlet of the plurality of tubes of the second reactor.

In an embodiment, a pressure at an inlet of the plurality of tubes ofthe second reactor (e.g., isothermal reactor) can be less than about 150psig (1.04 MPa), alternatively between about 75 psig (0.53 MPa) andabout 100 psig (0.69 MPa), alternatively between about 25 psig (0.17MPa) and about 70 psig (0.48 MPa), between about 30 psig (0.21 MPa) andabout 60 psig (0.41 MPa), or alternatively between about 35 psig (0.24MPa) and about 50 psig (0.34 MPa). Generally, a lower overall pressurecan result in a higher conversion to aromatic hydrocarbons, since thenaphtha reforming reactions results in a large net increase in moles. Alower overall pressure drop in the reactor system for carrying out anaphtha reforming process as disclosed herein can also be achieved byeliminating the use of a sulfur converter adsorber (SCA), as the SCA cancontribute to almost 10% of the overall pressure drop in the reactorsystem.

In an embodiment, the catalyst can have a crush strength of equal to orgreater than about 4 pounds force (lbf, 17.8 N), alternatively equal toor greater than about 5 lbf (22.2 N), alternatively equal to or greaterthan about 6 lbf (26.7 N), wherein the catalyst has a particle size ofabout 1/16^(th) inch (16 mm) in diameter. For purposes of the disclosureherein, the crush strength can be defined as the resistance of thecatalyst support and/or catalyst (e.g., catalyst particles) tocompressive forces, without experiencing mechanical failure.Measurements of crush strength are intended to provide an indication ofthe ability of the catalyst to maintain its physical integrity duringhandling and use. Crush strength can be determined in accordance withASTM method D 6175-98 “Standard Test Method for Radial Crush Strength ofExtruded Catalyst,” with the exception that the force applied to thesample is applied laterally. As will be appreciated by one of skill inthe art, and with the help of this disclosure, the ability to have atube loaded with catalyst can be limited by the height of the loadedcatalyst column, and the pressure drop across the reactor when thepressure contributes to the force exerted on the catalyst.

In an embodiment, at least one tube of the plurality of tubes of thesecond reactor (e.g., isothermal reactor) has a plurality of catalystzones. In an embodiment, an amount of the second naphtha reformingcatalyst of the isothermal reactor can be configured to be substantiallyfully utilized when the second naphtha reforming catalyst disposedwithin the plurality of tubes is operating above an endothermic reactionthreshold temperature, wherein the endothermic reaction thresholdtemperature can be about 800° F. (425° C.).

In an embodiment, at least one tube of the plurality of tubes of thesecond reactor (e.g., isothermal reactor) comprises a graded catalystbed, where the catalyst bed is graded with respect to the catalystparticle size and/or catalyst activity. Generally, the use of a gradedbed with respect to the catalyst particle size can be used to controlthe pressure drop across the plurality of tubes of the second reactor.Further, the use of a graded bed with respect to the catalyst activitycan allow for controlling the overall rate of reaction along a length ofa catalyst bed. For example, when the catalyst bed comprises a naphthareforming catalyst, if the zone of the catalyst bed that the hydrocarbonfeed stream encounters first has a high catalytic activity, then thereforming reaction can proceed at a very high rate causing a large dropin temperature, which can trigger a lower than desired reaction rate insubsequent zones of the catalyst bed.

In an embodiment, the plurality of tubes of the second reactor (e.g.,isothermal reactor) comprises a graded catalyst bed, where the catalystbed is graded with respect to the catalyst particle size. In anembodiment, at least one tube of the plurality of tubes of the secondreactor (e.g., isothermal reactor) comprises a graded catalyst bed,where the catalyst bed is graded with respect to the catalyst particlesize.

In an embodiment, the naphtha reforming catalyst (e.g., a first naphthareforming catalyst, a second naphtha reforming catalyst, etc.) can havea catalyst particle size of from about 0.01 inches (0.25 mm) to about0.5 inches (12.7 mm), alternatively from about 0.05 inches (1.27 mm) toabout 0.35 inches (8.89 mm), or alternatively from about 0.0625 inches(1.59 mm) to about 0.25 inches (6.35 mm). Generally, the catalyst bedinside the plurality of tubes of the second reactor (e.g., isothermalreactor) can comprise catalyst particles having a size decreasing alonga length of at least one tube of the plurality of tubes, from an inletof the plurality of tubes towards an outlet of the plurality of tubes,and in the direction of the flow inside the tubes. For example, thecatalyst particles can be characterized by a size gradient, where acatalyst particle size can decrease from an entry point into a catalystbed (e.g., inlet) to an exit point from the catalyst bed (e.g., outlet),e.g., a size of the catalyst particles can decrease along a catalyst bedin the direction of the flow through the tube comprising the catalystparticles. In some embodiments, a decrease in the size of the catalystparticles can be continuous (e.g., according to any gradient(s)) along alength of the fixed bed or zone thereof. In other embodiments, thedecrease in the size of the catalyst particles can occur step-wisethrough a plurality of zones across a length of the fixed bed whereinthe catalyst particles size composition (or distribution of catalystparticles sizes) of the individual zones is constant. As anotherexample, a size of the catalyst particles can decrease along someregions or zones of the catalyst bed, and stay the same along yet otherzones of the catalyst bed.

In an embodiment, the catalyst bed can comprise a plurality of catalystzones, where a first catalyst zone of the plurality of catalyst zonescan comprise a first catalyst material having a first particle size,where a second catalyst zone of the plurality of catalyst zones cancomprise a second catalyst material having a second particle size, wherethe first particle size can be larger than the second particle size, andwhere the first catalyst zone can be upstream of the second catalystzone. The first reactor effluent can contact the catalyst particles inthe first catalyst zone of the plurality of catalyst zones to produce afirst catalyst zone effluent, where the first catalyst zone is the firstzone of the plurality of catalyst zones contacted by the first reactoreffluent. The first catalyst zone effluent can contact the catalystparticles in the second catalyst zone of the plurality of catalyst zonesto produce a second catalyst zone effluent, which can then be recoveredas the second reactor effluent in embodiments where the catalyst bedcomprises only two catalyst zones, a first catalyst zone and a secondcatalyst zone. In embodiments where the catalyst bed comprises more thantwo catalyst zones, the second catalyst zone effluent can be furtherintroduced to the next catalyst zone, and so on. In some embodiments,the first particle size can be about 0.125 inches (3.18 mm), and thesecond particle size can be about 0.0625 inches (1.59 mm). Anysubsequent zones, if present, could have further decreasing catalystparticle sizes.

An embodiment of a graded catalyst bed 600 is shown in FIG. 6A. Thegraded catalyst bed 600 can be housed in a tube 602 (e.g., a tube of theplurality of tubes of the second reactor), and can comprise a topcatalyst zone 610, and a bottom catalyst zone 612, where the flow in thereactor can be from the top catalyst zone 610 to the bottom catalystzone 612. The top catalyst zone 610 can comprise a first catalystmaterial 620 having a first particle size, and the bottom catalyst zone612 can comprise the second catalyst material 622 having the secondparticle size, where the first particle size is larger than the secondparticle size.

Another embodiment of a graded catalyst bed 650 is shown in FIG. 6B. Thegraded catalyst bed 650 can be housed in a tube 602 (e.g., a tube of theplurality of tubes of the second reactor), and can comprise a topcatalyst zone 660 (e.g., a first zone), a middle catalyst zone 662, anda bottom catalyst zone 664 (e.g., a final zone), where the flow in thereactor can be from the top catalyst zone 660 towards the bottomcatalyst zone 664, and where the middle catalyst zone 662 can be locatedbetween the top catalyst zone 660 and the bottom catalyst zone 664. Thetop catalyst zone 660 can comprise a first catalyst material 620 havinga first particle size. The bottom catalyst zone 664 can comprise asecond catalyst material 622 having a second particle size, where thefirst particle size is larger than the second particle size. The middlecatalyst zone 662 can comprise both the first catalyst material 620having the first particle size and the second catalyst material 622having the second particle size. In some embodiments, the middlecatalyst zone 662 can comprise the first catalyst material 620 and thesecond catalyst material in about the same amounts by volume, thoughhigher or lower relative volumetric amounts can also be used. In anembodiment, the middle catalyst zone 662 can comprise the first catalystmaterial 620 and the second catalyst material in a ratio of about 45/55,about 50/50, about 55/45, based on volumetric ratios of the firstcatalyst material 620 to the second catalyst material 622 in the middlecatalyst zone 662.

In an embodiment, the plurality of tubes of the second reactor (e.g.,isothermal reactor) comprises a graded catalyst bed, where the catalystbed is graded with respect to the catalyst loading and/or activity. Inan embodiment, at least one tube of the plurality of tubes of the secondreactor (e.g., isothermal reactor) comprises a graded catalyst bed,where the catalyst bed is graded with respect to the catalyst loadingand/or activity. The catalyst bed can be graded by the loading of acatalytically active metal (e.g., group VIII metal, group IB metal, Pt,etc.), and/or by the loading of an inert diluent to a fixed catalystcomposition. In some aspects where the catalyst grading occurs via metalloading, no inert diluent is used. In an embodiment, a top catalyst zonecan comprise from about 0.5 wt. % to about 0.60 wt. % catalyticallyactive metal (e.g., group VIII metal, group IB metal, Pt, etc.), amiddle catalyst zone can comprise from about 0.75 wt. % to about 0.90wt. % catalytically active metal (e.g., group VIII metal, group IBmetal, Pt, etc.), and a bottom catalyst zone can comprise from about 1.0wt. % to about 1.25 wt. % catalytically active metal (e.g., group VIIImetal, group IB metal, Pt, etc.). As will be appreciated by one of skillin the art, and with the help of this disclosure, the ranges ofcatalytically active metal (e.g., group VIII metal, group IB metal, Pt,etc.) loading in each of the top, middle, and bottom zones can vary asnecessary for each individual naphtha reforming process.

In an embodiment, the catalyst bed (e.g., graded catalyst bed) insidethe plurality of tubes of the second reactor (e.g., isothermal reactor)can comprise catalyst particles having an amount of active catalystmaterial per unit volume (e.g., volumetric concentration of activecatalyst material) increasing along a length of at least one tube of theplurality of tubes, from an inlet to the plurality of tubes towards anoutlet of the plurality of tubes, and in the direction of the flowinside the tubes, where the balance of the material per unit volume canbe an inert material, a less active naphtha reforming catalyst material,an isomerization catalyst, or a mixture of both.

In an embodiment, the inert material of the graded catalyst bed can beany suitable chemically inert solid diluent or bulking material thatdoes not catalyze the naphtha reforming reactions. For example, theinert material can be any support described herein for the naphthareforming catalyst, such as a zeolite and one or more halides, withoutthe at least one group VIII metal. In some embodiments, the inertmaterial can comprise alumina, preferably silica, alpha alumina,silica-alumina, fused alumina, aluminosilicates, glass beads, and thelike, or combinations thereof.

In an embodiment, the last catalyst zone (e.g., second catalyst zone,bottom catalyst zone, third catalyst zone, fourth catalyst zone) insidethe plurality of tubes of the second reactor (e.g., isothermal reactor)can comprise isomerization catalyst particles. In an embodiment, theisomerization catalyst can be any suitable isomerization catalystmaterial that has a higher activity for the naphtha isomerizationreactions than the naphtha reforming catalyst, particularly for theisomerization of branched hydrocarbons to less branched hydrocarbons; orany suitable isomerization catalyst material that catalyzes to a lesserextent the naphtha reforming reactions when compared to the naphthareforming catalyst (e.g., a less active naphtha reforming catalystmaterial). As will be appreciated by one of skill in the art, and withthe help of this disclosure, if the isomerization catalyst was placed inthe first reaction zone, then the isomerization catalyst would catalyzethe reaction of the large excess of unbranched hydrocarbons (e.g.,convertible hydrocarbons) into much-much less reactive branchedhydrocarbons. However, and as will be appreciated by one of skill in theart, and with the help of this disclosure, if the isomerization catalystis placed in the last reaction zone, subsequent to substantially all theunbranched hydrocarbons having been converted, the isomerizationcatalyst can catalyze the conversion of branched hydrocarbons into (thenow depleted) unbranched hydrocarbons.

The isomerization catalyst can catalyze the conversion of acyclichydrocarbons to cyclic hydrocarbons, but should not have high activityor activity towards dehydrogenating the cyclic hydrocarbons to producearomatic hydrocarbons. In some embodiments, the isomerization catalystcan comprise a zeolite support, and one or more halides. The zeolitesupport, and one or more halides can be any suitable zeolitic supportsand halides as described herein for the naphtha reforming catalyst,without the at least one group VIII metal. In an aspect, theisomerization catalysts can be used for isomerizing dimetylbutanes toconvertible C₆s.

In an embodiment, the catalyst bed (e.g., graded catalyst bed) cancomprise a plurality of catalyst zones, where a first catalyst zone ofthe plurality of catalyst zones can comprise a mixture of a naphthareforming catalyst, a less active naphtha reforming catalyst material,and an inert material, or a mixture of both, and where the firstcatalyst zone can be disposed on an upstream end of the at least onetube within the reactor furnace. In some embodiments, the catalyst bedcan comprise a second catalyst zone of the plurality of catalyst zoneswhere the second catalyst zone can comprise only a catalyst without theinert material, and where the second catalyst zone can be disposeddownstream of the first catalyst zone. Each catalyst zone of theplurality of catalyst zones comprises an increasing amount of catalystparticles (e.g., an increasing volumetric concentration of activecatalyst material) from an upstream to a downstream direction, where afinal catalyst zone of the plurality of catalysts zones contains thelowest amount (e.g., little to none) of inert material, and where thefinal catalyst zone is the most downstream catalyst zone of theplurality of catalyst zones.

In some embodiments, the catalyst bed (e.g., graded catalyst bed) insidethe plurality of tubes of the second reactor (e.g., isothermal reactor)can comprise two or more zones (e.g., catalytic zones), where the firstzone and subsequent zones comprises the naphtha reforming catalyst andoptionally an inert material, a less active naphtha reforming catalystmaterial, or mixtures thereof. In such an embodiment, the last zonecomprises the naphtha reforming catalyst and optionally an inertmaterial, an isomerization catalyst, or mixtures thereof. When thecatalyst bed comprises two or more zones (e.g., catalytic zones), thenaphtha reforming catalyst can be distributed along the catalyst bedaccording to a volumetric concentration gradient. For example, avolumetric concentration of the naphtha reforming catalyst can increasefrom an entry point into a catalyst bed (e.g., inlet) to an exit pointfrom the catalyst bed (e.g., outlet), e.g., a volumetric concentrationof the naphtha reforming catalyst can increase along a catalyst bed inthe direction of the flow through the isothermal reactor. In someembodiments, an increase in the volumetric concentration of the naphthareforming catalyst can be continuous along a length of the catalyst bedor zone thereof. In other embodiments, the increase in the volumetricconcentration of the naphtha reforming catalyst can be step-wise acrossa length of the catalyst bed or zone thereof. As another example, avolumetric concentration of the naphtha reforming catalyst can increasealong some regions or zones of the catalyst bed, and stay the same alongyet other regions of the catalyst bed. The amount of inert material,less active naphtha reforming catalyst material, an isomerizationcatalyst, or a mixture of both can likewise be adjusted or varied acrossthe catalyst bed geometry (e.g., along a length of the catalyst bed orzone thereof) to provide a desired naphtha reforming catalyst volumetricconcentration profile.

In an embodiment, the catalyst bed (e.g., graded catalyst bed) insidethe plurality of tubes of the second reactor (e.g., isothermal reactor)can comprise a top zone, a middle zone, and a bottom zone, where theflow in the reactor can be from a top zone towards a bottom zone, andwhere the middle zone can be located between the top zone and the bottomzone. In such embodiment, the top zone comprises both a naphthareforming catalyst and an inert material, a less active naphthareforming catalyst material, or a mixtures thereof, where an amount ofnaphtha reforming catalyst by volume is about the same as (e.g., about45/55, about 50/50, about 55/45, based on volumetric ratios of naphthareforming catalyst to inert material, less active naphtha reformingcatalyst material, or a mixture of both in the top zone) or less then(e.g., less than 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or 5%,based on a total volume of the top zone) an amount of inert material,less active naphtha reforming catalyst material, or a mixture of both inthe top zone; where the middle zone comprises an inert material, a lessactive naphtha reforming catalyst material, or a mixture of both in anamount by volume that is less than (e.g., less than 50%, 45%, 40%, 35%,30%, 25%, 20%, 15%, 10%, 5%, or 1%, based on a total volume of themiddle zone) an amount of the naphtha reforming catalyst; and where anamount of the naphtha reforming catalyst by volume is greater than(e.g., greater than 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%,99%, or 100% based on a total volume of the bottom zone) an amount ofthe inert material, less active naphtha reforming catalyst material, ormixture of both in the bottom zone. In such embodiment, the middlecatalyst zone comprises both a naphtha reforming catalyst and an inertmaterial, a less active naphtha reforming catalyst material, or mixturesthereof. In such embodiments, the bottom catalyst zone comprises both anaphtha reforming catalyst and an inert material, a less active naphthareforming catalyst material, an isomerization catalyst, or a mixturethereof.

In an embodiment, the naphtha reforming catalyst can be present in thegraded catalyst bed or any zone thereof in an amount of from about 10vol. % to about 100 vol. %, alternatively from about 25 vol. % to about100 vol. %, or alternatively from about 33 vol. % to about 66 vol. %,based on the total volume of the catalyst bed or zone thereof.

In an embodiment, the catalyst bed (e.g., graded catalyst bed) insidethe plurality of tubes of the second reactor (e.g., isothermal reactor)can comprise a top zone, a middle zone, and a bottom zone; where the topzone includes from about 50 vol. % to about 60 vol. % of a naphthareforming catalyst and from about 40 vol. % to about 50 vol. % inertmaterial, less active naphtha reforming catalyst material, or mixture ofboth by volume; where the middle zone includes from about 80 vol. % toabout 60 vol. % of a naphtha reforming catalyst and from about 20 vol. %to about 40 vol. % of an inert material, less active naphtha reformingcatalyst material, or mixture of both by volume; and where the bottomzone includes about 100 vol. % reforming catalyst by volume.

In another embodiment, the catalyst bed (e.g., graded catalyst bed)inside the plurality of tubes of the second reactor (e.g., isothermalreactor) can comprise a top zone, a middle zone, and a bottom zone;where the top zone includes from about 50 vol. % to about 60 vol. % of anaphtha reforming catalyst and from about 40 vol. % to about 50 vol. %inert material, less active naphtha reforming catalyst material, ormixture of both by volume; where the middle zone includes from about 80vol. % to about 60 vol. % of a naphtha reforming catalyst and from about20 vol. % to about 40 vol. % of an inert material, less active naphthareforming catalyst material, or mixture of both by volume; and where thebottom zone includes from about 100 vol. % to about 20 vol. % naphthareforming catalyst by volume and from about 0 vol. % to about 20 vol. %of an isomerization catalyst material.

In an embodiment, the catalyst bed (e.g., graded catalyst bed) cancomprise a plurality of catalyst zones, where a first catalyst zone ofthe plurality of catalyst zones can comprise a mixture of catalystparticles (e.g., naphtha reforming catalyst particles) and a firstmaterial (e.g., an inert material, a less active naphtha reformingcatalyst material, or a mixture of both), and where the first catalystzone can be disposed on an upstream end of the at least one tube withinthe reactor furnace.

In an embodiment, the first reactor effluent recovered from theadiabatic reactor can pass through a plurality of catalyst zones withinat least one tube of the plurality of tubes of the second reactor (e.g.,isothermal reactor) while being heated in the reactor furnace. The firstreactor effluent can contact a mixture of catalyst particles and a firstmaterial in a first catalyst zone of the plurality of catalyst zones,where the first catalyst zone is the first catalyst zone of theplurality of catalyst zones contacted by the first reactor effluent,where the first reactor effluent contacts a second mixture of catalystparticles and the first material in a second catalyst zone of theplurality of catalyst zones, and where a ratio of the volume of catalystparticles to the volume of the first material is higher in the secondcatalyst zone than in the first catalyst zone.

In an embodiment, the first reactor effluent can contact the mixture ofcatalyst particles and the first material in the first catalyst zone ofthe plurality of catalyst zones to produce a first catalyst zoneeffluent, where the first catalyst zone is the first catalyst zone ofthe plurality of catalyst zones contacted by the first reactor effluent.The first catalyst zone effluent can contact a second catalyst zone ofthe plurality of catalyst zones containing a second mixture of catalystparticles and a second material (e.g., an inert material, a less activenaphtha reforming catalyst material, or a mixture of both), where aweight ratio of the amount of catalyst particles to the second materialis higher in the second catalyst zone than a weight ratio of the amountof the catalyst particles to the first material in the first catalystzone, where the first catalyst zone is upstream of the second catalystzone, and where the first material and the second material can be thesame or different. These weight ratios are based on the weight of thecatalyst when loaded. The second catalyst zone effluent can contact theremaining catalyst zones of the plurality of catalyst zones, where eachcatalyst zone of the plurality of catalyst zones comprises an increasingamount of catalyst particles from an upstream to a downstream direction,and where a final catalyst zone of the plurality of catalysts zonescontains no first material and/or second material, where the finalcatalyst zone is the most downstream catalyst zone of the plurality ofcatalyst zones.

In an embodiment, the first reactor effluent contacts naphtha reformingcatalyst particles in a first catalyst zone of the plurality of catalystzones to produce a first catalyst zone effluent, wherein the firstcatalyst zone is the first catalyst zone of the plurality of catalystzones contacted by the first reactor effluent; wherein the firstcatalyst zone effluent contacts a second catalyst zone of the pluralityof catalyst zones to produce a second catalyst zone effluent, whereinthe second catalyst zone contains a second zone mixture of naphthareforming catalyst particles and a second material, wherein the firstcatalyst zone is upstream of the second catalyst zone; and wherein thesecond catalyst zone effluent contacts a third catalyst zone of theplurality of catalyst zones to produce a third catalyst zone effluent,wherein the third catalyst zone contains naphtha reforming catalystparticles or a third zone mixture of naphtha reforming catalystparticles and a third material, wherein the third catalyst zone isdownstream of the second catalyst zone, and wherein the third catalystzone is the last catalyst zone of the plurality of catalyst zonescontacted by the first reactor effluent. In such embodiment, the thirdzone mixture comprises an inert material, an isomerization catalyst, ora mixture of both an inert material and an isomerization catalyst. Insuch embodiment, at least a catalyst zone upstream of the third catalystzone comprises substantially naphtha reforming catalyst particles.

In another embodiment, the first reactor effluent contacts a firstcatalyst zone of the plurality of catalyst zones to produce a firstcatalyst zone effluent, wherein the first catalyst zone contains a firstzone mixture of naphtha reforming catalyst particles and a firstmaterial, wherein the first catalyst zone is the first catalyst zone ofthe plurality of catalyst zones contacted by the first reactor effluent;wherein the first catalyst zone effluent contacts a second catalyst zoneof the plurality of catalyst zones to produce a second catalyst zoneeffluent, wherein the second catalyst zone contains naphtha reformingcatalyst particles, wherein the first catalyst zone is upstream of thesecond catalyst zone; and wherein the second catalyst zone effluentcontacts a third catalyst zone of the plurality of catalyst zones toproduce a third catalyst zone effluent, wherein the third catalyst zonecontains naphtha reforming catalyst particles or a third zone mixture ofnaphtha reforming catalyst particles and a third material, wherein thethird catalyst zone is downstream of the second catalyst zone, andwherein the third catalyst zone is the last catalyst zone of theplurality of catalyst zones contacted by the first reactor effluent. Insuch embodiment, the third zone mixture comprises an inert material, anisomerization catalyst, or a mixture of both an inert material and anisomerization catalyst. In such embodiment, at least a catalyst zoneupstream of the third catalyst zone comprises substantially naphthareforming catalyst particles.

An embodiment of a graded catalyst bed 700 is shown in FIG. 7A. Thegraded catalyst bed 700 can be housed in a tube 702 (e.g., a tube of theplurality of tubes of the second reactor), and can comprise a topcatalyst zone 710, and a bottom catalyst zone 712, where the flow in thereactor can be from the top catalyst zone 710 to the bottom catalystzone 712. The top catalyst zone 710 can comprise a naphtha reformingcatalyst 720 and a first material 722, where the first material cancomprise an inert material, a less active naphtha reforming catalystmaterial, or a mixture of both, and where a concentration of the naphthareforming catalyst 720 per unit volume is about the same as aconcentration of the first material 722 per unit volume in the firstcatalyst zone. The bottom catalyst zone 712 can comprise the naphthareforming catalyst 720 and no first material.

Another embodiment of a graded catalyst bed 750 is shown in FIG. 7B. Thegraded catalyst bed 750 can be housed in a tube 702 (e.g., a tube of theplurality of tubes of the second reactor), and can comprise a topcatalyst zone 760 (e.g., a first zone), a middle catalyst zone 762, anda bottom catalyst zone 764 (e.g., a final zone), where the flow in thereactor can be from the top catalyst zone 760 towards the bottomcatalyst zone 764, and where the middle catalyst zone 762 can be locatedbetween the top catalyst zone 760 and the bottom catalyst zone 764. Thetop catalyst zone 760 can comprise a naphtha reforming catalyst 720 anda first material 722, where the first material can comprise an inertmaterial, a less active naphtha reforming catalyst material, or amixture of both, and where a concentration of the naphtha reformingcatalyst 720 per unit volume is about the same as a concentration of thefirst material 722 per unit volume in the top catalyst zone. The middlecatalyst zone 762 can comprise the naphtha reforming catalyst 720 andthe first material 722, where a concentration of the naphtha reformingcatalyst 720 per unit volume is greater than a concentration of thefirst material 722 per unit volume in the middle catalyst zone (e.g., aratio of a concentration of the naphtha reforming catalyst 720 per unitvolume to a concentration of the first material 722 per unit volume inthe middle catalyst zone is about 2:1). The bottom catalyst zone 764 cancomprise the naphtha reforming catalyst 720 and no first material.

In an embodiment, the plurality of tubes of the second reactor (e.g.,isothermal reactor) comprises a graded catalyst bed, where the catalystbed is graded with respect to both the catalyst particle size and thecatalyst loading and/or activity. In an embodiment, at least one tube ofthe plurality of tubes of the second reactor (e.g., isothermal reactor)comprises a graded catalyst bed, where the catalyst bed is graded withrespect to both the catalyst particle size and the catalyst loadingand/or activity. The catalyst bed can be graded with respect to thecatalyst particle size as previously described herein and concurrentlywith respect to the catalyst loading and/or activity as previouslydescribed herein.

In an embodiment, the catalyst bed inside the plurality of tubes of thesecond reactor (e.g., isothermal reactor) can comprise catalystparticles having (i) a size decreasing along a length of at least onetube of the plurality of tubes, from an inlet to the plurality of tubestowards an outlet of the plurality of tubes, and in the direction of theflow inside the tubes; and (ii) an amount of active catalyst materialper unit volume (e.g., volumetric concentration of active catalystmaterial) increasing along a length of at least one tube of theplurality of tubes, from an inlet to the plurality of tubes towards anoutlet of the plurality of tubes, and in the direction of the flowinside the tubes, where the balance of the material per unit volume canbe an inert material, a less active naphtha reforming catalyst material,an isomerization catalyst, or mixtures thereof.

In an embodiment, the catalyst bed (e.g., graded catalyst bed) cancomprise a plurality of catalyst zones, where a first catalyst zone ofthe plurality of catalyst zones can comprise a mixture of catalystparticles (e.g., naphtha reforming catalyst particles) having a firstcatalyst particle size and a first material (e.g., an inert material, aless active naphtha reforming catalyst material, or a mixture of both)having a first material particle size, and where the first catalyst zonecan be disposed on an upstream end of the at least one tube within thereactor furnace. The catalyst bed can comprise a second catalyst zone,where the second catalyst zone of the plurality of catalyst zones cancomprise only a second catalyst material having a second catalystparticle size, without the inert material, where the first particle sizecan be larger than the second particle size, and where the firstcatalyst zone can be upstream of the second catalyst zone. In someembodiments, the first catalyst particle size and the first materialparticle size can be the same. In other embodiments, the first catalystparticle size and the first material particle size can be different.Each catalyst zone of the plurality of catalyst zones comprises anincreasing amount of catalyst particles (e.g., an increasing volumetricconcentration of active catalyst material) from an upstream to adownstream direction, where a final catalyst zone of the plurality ofcatalysts zones contains no inert material, where the catalyst particlesdecrease in size from an upstream to a downstream direction, and wherethe final catalyst zone is the most downstream catalyst zone of theplurality of catalyst zones.

An embodiment of a graded catalyst bed 800 is shown in FIG. 8A. Thegraded catalyst bed 800 can be housed in a tube 802 (e.g., a tube of theplurality of tubes of the second reactor), and can comprise a topcatalyst zone 810, and a bottom catalyst zone 812, where the flow in thereactor can be from the top catalyst zone 810 to the bottom catalystzone 812. The top catalyst zone 810 can comprise a naphtha reformingcatalyst 820 having a first particle size and a first material 822having the first particle size, where the first material can comprise aninert material, a less active naphtha reforming catalyst material, or amixture of both, and where a concentration of the naphtha reformingcatalyst 820 per unit volume is about the same as a concentration of thefirst material 822 per unit volume in the first catalyst zone. Thebottom catalyst zone 812 can comprise a naphtha reforming catalyst 821having a second particle size and no first material, where the firstparticle size is larger than the second particle size.

Another embodiment of a graded catalyst bed 850 is shown in FIG. 7B. Thegraded catalyst bed 850 can be housed in a tube 802 (e.g., a tube of theplurality of tubes of the second reactor), and can comprise a topcatalyst zone 860 (e.g., a first zone), a middle catalyst zone 862, anda bottom catalyst zone 864 (e.g., a final zone), where the flow in thereactor can be from the top catalyst zone 860 towards the bottomcatalyst zone 864, and where the middle catalyst zone 862 can be locatedbetween the top catalyst zone 860 and the bottom catalyst zone 864. Thetop catalyst zone 860 can comprise a naphtha reforming catalyst 820having a first particle size and a first material 822 having the firstparticle size, where the first material can comprise an inert material,a less active naphtha reforming catalyst material, or a mixture of both,and where a concentration of the naphtha reforming catalyst 820 per unitvolume is about the same as a concentration of the first material 822per unit volume in the top catalyst zone. The middle catalyst zone 862can comprise the naphtha reforming catalyst 820 having the firstparticle size, the naphtha reforming catalyst 821 having a secondparticle size, the first material 822 having the first particle size,and a first material 823 having the second particle size, where aconcentration of the naphtha reforming catalyst per unit volume isgreater than a concentration of the first material per unit volume inthe middle catalyst zone (e.g., a ratio of a concentration of thenaphtha reforming catalyst per unit volume to a concentration of thefirst material per unit volume in the middle catalyst zone is about2:1); and where the first particle size is larger than the secondparticle size. The bottom catalyst zone 864 can comprise the naphthareforming catalyst 821 having the second particle size and no firstmaterial.

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can further comprise processing the hydrocarbon feedstream with a preliminary reactor (e.g., sulfur sorber unit), where thepreliminary reactor contains a sulfur control sorbent (e.g., sulfuradsorbing material) alone or in combination with a sulfur convertingmaterial, and where the sulfur control sorbent can remove a portion ofthe sulfur in the hydrocarbon feed stream and the sulfur convertingmaterial can convert a portion of the sulfur in the hydrocarbon feedstream to a material more readily adsorbed by the sulfur controlsorbent. The preliminary reactor processes the hydrocarbon feed streamprior to introducing the hydrocarbon feed stream to the first reactor(e.g., adiabatic reactor). The preliminary reactor (e.g., sulfur sorberunit) may also act as a precaution or backup in case any upstreamhydrotreating system fails or has an operating upset. The preliminaryreactor unit may be used to reduce the amount of sulfur in thehydrocarbon feed stream and may comprise any suitable sulfur converteradsorber capable of removing sulfur from the hydrocarbon feed stream. Inan embodiment, the preliminary reactor unit can be in fluidcommunication with the first inlet of the first reactor (e.g., adiabaticreactor). The preliminary reactor unit can be upstream of the firstfurnace, where the first furnace can be configured to heat thehydrocarbon feed stream prior to the hydrocarbon feed stream enteringthe first inlet of the first reactor.

In an embodiment, the bed of the sulfur adsorbing material can compriseany suitable sulfur adsorbing material. The sulfur adsorbing materialcan comprise a base on a substrate, where the substrate can comprise aninorganic oxide, such as alumina, silica, aluminosilicates, zeolites,and the like, or combinations thereof. The base can comprise anysuitable hydroxide, such as sodium hydroxide, potassium hydroxide,ammonium hydroxide, tetraalkylammonium hydroxide, lithium, copper, zincoxide, and the like, or combinations thereof. In an embodiment, thesulfur adsorbing material can comprise potassium hydroxide on alumina.In some embodiments, the sulfur adsorbing material can comprise thefirst naphtha reforming catalyst, the second naphtha reforming catalyst,the third reforming catalyst, or combinations thereof.

In an embodiment, the bed of the sulfur adsorbing material can bepreceded by a bed of a sulfur converting material. The sulfur convertingmaterial can comprise any suitable material that can convert thesulfur-containing compounds present in the hydrocarbon feed stream. Thesulfur converting material can comprise at least one group VIII metal onan inorganic oxide substrate, such as alumina, silica, aluminosilicates,zeolites, and the like, or combinations thereof. The at least one groupVIII metal can comprise Pt, Pd, Ni, Co, and the like, or combinationsthereof. In an embodiment, the sulfur converting material can comprisePt on alumina.

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can further comprise passing the hydrocarbon feedstream through a preliminary reactor, where the preliminary reactorcontains a sulfur control sorbent (e.g., sulfur adsorbing material)alone or in combination with a sulfur converting material, and where thesulfur control sorbent can remove a portion of the sulfur in thehydrocarbon feed stream and the sulfur converting material can convert aportion of the sulfur in the hydrocarbon feed stream to a material morereadily adsorbed by the sulfur control sorbent. In such embodiment, themethod can further comprise (i) detecting a first sulfur level in thehydrocarbon feed stream upstream of the preliminary reactor; (ii)detecting a second sulfur level in the hydrocarbon feed streamdownstream of the preliminary reactor; and (iii) ceasing theintroduction of the hydrocarbon feed stream to the first reactor when areduction in a sulfur level between the first sulfur level and thesecond sulfur level is less than a threshold. Sulfur levels can bemonitored (e.g., detected) by using on-stream sulfur analyzers.

An embodiment of a general naphtha reforming process 900 is shown inFIG. 9A. At the inlet of the process, a preliminary hydrocarbon feedstream is fed through line 901 to a preliminary reactor 903 to produce ahydrocarbon feed stream, where the preliminary reactor 903 comprises abed of sulfur control sorbent 904, and where the preliminary reactor canbe a radial flow reactor. In some embodiments, the bed of sulfur controlsorbent 904 can comprise an optional top portion 904 a of the bedcomprising a sulfur converting material and a bottom portion 904 b ofthe bed comprising a sulfur adsorbing material. In some aspects, the topportion 904 a and the bottom portion 904 b can be two distinct beds. Inother aspects, the top portion 904 a and the bottom portion 904 b can betwo different zones within the same bed. In other embodiments, the bedof sulfur control sorbent 904 can comprise substantially sulfuradsorbing material. In yet other embodiments, the bed 904 can comprise acombination of a sulfur control and sulfur absorber material, whereinthe bed 904 can be a single bed. The preliminary reactor 903 can includeany of the adiabatic reactors described herein. The preliminaryhydrocarbon feed stream can be characterized by a first sulfur level ofequal to or greater than about 50 ppbw, alternatively equal to orgreater than about 100 ppbw, or alternatively equal to or greater thanabout 200 ppbw. The first sulfur level of the preliminary hydrocarbonfeed stream can be monitored (e.g., detected) in the line 901. Thehydrocarbon feed stream can be characterized by a second sulfur level ofless than about 50 ppbw, alternatively less than about 40 ppbw, oralternatively less than about 25 ppbw. The second sulfur level of thehydrocarbon feed stream can be monitored (e.g., detected) in the line902. In embodiments where the second sulfur level of the hydrocarbonfeed stream is above 50 ppmw, the flow of hydrocarbon feed streamthrough line 902 towards the first reactor 910 can be interrupted, andan alternative hydrocarbon feed stream that has a sulfur level below 50ppbw can be introduced to line 902. The alternative hydrocarbon feedstream can be a hydrocarbon feed stream that is introduced to anotherpreliminary reactor (not shown in FIG. 9) to bypass the preliminaryreactor 903. The hydrocarbon feed stream passing through line 902 can beheated in a first furnace 908 to increase the temperature of thehydrocarbon feed stream. The heated hydrocarbon feed stream passingthrough line 909 can be introduced to a first reactor 910, where thefirst reactor 910 can be an adiabatic radial flow reactor comprising acatalyst bed 912 disposed therein, and where the catalyst bed 912 cancomprise a first naphtha reforming catalyst. The first reactor 910 caninclude any of the adiabatic reactors described herein. At least aportion of the convertible hydrocarbons in the hydrocarbon feed streamcan be converted to aromatic hydrocarbons in the first reactor 910 toform a first reactor effluent. In some embodiments, the first reactoreffluent passing through line 916 can be heated in a second furnace 920to increase the temperature of the first reactor effluent. The heatedfirst reactor effluent passing through line 922 can be introduced to asecond reactor 940, where the second reactor 940 can operate underisothermal naphtha reforming conditions. In other embodiments, the firstreactor effluent passing through line 916 a can be heated in aconvection zone 930 of a reactor furnace 945 to further increase thetemperature of the first reactor effluent. For example, the firstreactor effluent passing through line 916 a can be heated in aconvection zone 930 of a reactor furnace 945 to a naphtha reformingtemperature. The heated first reactor effluent passing through line 923can be introduced to a second reactor 940, where the second reactor 940can operate under isothermal naphtha reforming conditions. The secondreactor 940 can include any of the isothermal reactors described herein.The second reactor 940 can comprise a plurality of tubes 942 having asecond naphtha reforming catalyst disposed therein, where the pluralityof tubes 942 can be disposed within a reactor furnace 945. The firstnaphtha reforming catalyst and the second naphtha reforming catalyst canbe the same or different. At least an additional portion of theconvertible hydrocarbons in the first reactor effluent can be convertedto aromatic hydrocarbons in the second reactor 940 to form a secondreactor effluent 944.

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can further comprise passing the hydrocarbon feedstream through a preliminary reactor (e.g., a third reactor) comprisinga third reforming catalyst prior to introducing the hydrocarbon feedstream to the first reactor (e.g., adiabatic reactor) comprising thefirst naphtha reforming catalyst, to produce a preliminary reactoreffluent, where the third catalyst can remove a portion of the sulfur inthe hydrocarbon feed stream, and where the first naphtha reformingcatalyst, the second naphtha reforming catalyst of a second reactor(e.g. isothermal reactor) downstream of the first reactor, and the thirdreforming catalyst can be the same or different. In such embodiment, themethod can further comprise (i) detecting a decrease in temperaturebetween the hydrocarbon feed stream and the preliminary reactoreffluent; and (ii) ceasing the introduction of the feed stream to thepreliminary reactor when the decrease in the temperature is less than athreshold. The third reforming catalyst of the preliminary reactor canserve a dual purpose of reforming a portion of the convertiblehydrocarbons of the hydrocarbon feed stream, and removing a portion ofthe sulfur in the hydrocarbon feed stream. The naphtha reformingreactions are highly endothermic, and as such a temperature of thepreliminary reactor effluent is lower than a temperature of thehydrocarbon feed stream prior to entering the preliminary reactor. Adecrease in catalytic activity of the third reforming catalyst can leadto the naphtha reforming reactions occurring at a lower extent, which inturn can translate in less of a temperature decrease between thehydrocarbon feed stream and the preliminary reactor effluent (e.g., ahigher temperature of the preliminary reactor effluent than expected). Adecrease in catalytic activity of the third reforming catalyst can bedue to the presence of sulfur in the hydrocarbon feed stream, e.g.,catalyst deactivation or poisoning by sulfur in the hydrocarbon feedstream. A decrease in catalytic activity of the third reforming catalystindicated by less of a temperature decrease between the hydrocarbon feedstream and the preliminary reactor effluent (e.g., increase in thepreliminary reactor effluent temperature) can generally indicate thatthe catalyst is spent and it should be rejuvenated.

In some embodiments, the third reactor comprising the third reformingcatalyst can be run in parallel with the first reactor comprising thefirst naphtha reforming catalyst, such that when either the firstnaphtha reforming catalyst or the third reforming catalyst becomesspent, the third reactor or the first reactor, respectively, couldcontinue the naphtha reforming process, thereby providing for acontinuous naphtha reforming process.

An embodiment of a general naphtha reforming process 950 is shown inFIG. 9B. At the inlet of the process, a hydrocarbon feed stream is fedthrough line 952. The hydrocarbon feed stream passing through line 952can be heated in a first furnace 958 to increase the temperature of thehydrocarbon feed stream. A first portion 959 a of the heated hydrocarbonfeed stream passing through line 959 can be introduced to a firstreactor 960, where the first reactor 960 can be an adiabatic radial flowreactor comprising a catalyst bed 962 disposed therein, and where thecatalyst bed 962 can comprise a first naphtha reforming catalyst. Atleast a portion of the convertible hydrocarbons in the heatedhydrocarbon feed stream passing through line 959 a can be converted toaromatic hydrocarbons in the first reactor 960 to form a first reactoreffluent. A second portion 959 b of the heated hydrocarbon feed streampassing through line 959 can be introduced to a third reactor 965, wherethe third reactor 965 can be an adiabatic radial flow reactor comprisinga catalyst bed 963 disposed therein, and where the catalyst bed 963 cancomprise a third reforming catalyst. The first reactor 960 and/or thethird reactor 965 can include any of the adiabatic reactors describedherein. At least a portion of the convertible hydrocarbons in the heatedhydrocarbon feed stream passing through line 959 b can be converted toaromatic hydrocarbons in the third reactor 965 to form a third reactoreffluent. A decrease in catalytic activity of the third reformingcatalyst indicated by less of a temperature decrease between thehydrocarbon feed stream passing through line 959 b and the third reactoreffluent passing through line 966 b (e.g., increase in the third reactoreffluent temperature) can generally indicate that the third reformingcatalyst is spent and a catalytic activity should be restored. In suchcase, the flow of heated hydrocarbon feed stream through line 959 b canbe shut off, along with the flow of third reactor effluent through line966 b, to isolate the third reactor and restore catalytic activity inthe third reactor 965. Similarly, a decrease in catalytic activity ofthe first naphtha reforming catalyst indicated by less of a temperaturedecrease between the hydrocarbon feed stream passing through line 959 aand the first reactor effluent passing through line 966 a (e.g.,increase in the first reactor effluent temperature) can generallyindicate that the first naphtha reforming catalyst is spent and acatalytic activity should be restored. In such case, the flow of heatedhydrocarbon feed stream through line 959 a can be shut off, along withthe flow of first reactor effluent through line 966 a, to isolate thefirst reactor and restore catalytic activity in the first reactor 960.In some embodiments, the adiabatic reactor effluent passing through line966 (e.g., the combined streams of first reactor effluent passingthrough line 966 a and the second reactor effluent passing through line966 b) can be heated in a second furnace 970 to increase the temperatureof the adiabatic reactor effluent. The heated adiabatic reactor effluentpassing through line 972 can be introduced to a second reactor 980,where the second reactor 980 can operate under isothermal naphthareforming conditions. In other embodiments, the adiabatic reactoreffluent passing through line 967 (e.g., the combined streams of firstreactor effluent passing through line 966 a and the second reactoreffluent passing through line 966 b) can be heated in a convection zone975 of a reactor furnace 990 to further increase the temperature of theadiabatic reactor effluent. For example, the adiabatic reactor effluentpassing through line 967 can be heated in a convection zone 975 of areactor furnace 990 to a naphtha reforming temperature. The heatedadiabatic reactor effluent passing through line 973 can be introduced toa second reactor 980, where the second reactor 980 can operate underisothermal naphtha reforming conditions. The second reactor 980 caninclude any of the isothermal reactors described herein. The secondreactor 980 can comprise a plurality of tubes 982 having a secondnaphtha reforming catalyst disposed therein, where the plurality oftubes 982 can be disposed within a reactor furnace 990. The firstnaphtha reforming catalyst and the second naphtha reforming catalyst canbe the same or different. At least an additional portion of theconvertible hydrocarbons in the adiabatic reactor effluent can beconverted to aromatic hydrocarbons in the second reactor 980 to form asecond reactor effluent 984.

In an embodiment, an increase in an outlet reactor temperature in thesecond reactor (e.g., isothermal reactor) could indicate a loss ofactivity for an endothermic reaction, e.g., could indicate that thenaphtha reforming catalyst in the second reactor (e.g., second naphthareforming catalyst) is spent and catalytic activity needs to berestored. In an embodiment, a method of carrying out a naphtha reformingprocess as disclosed herein can further comprise (i) ceasing the passingof the first reactor effluent to the isothermal reactor; (ii)rejuvenating the second naphtha reforming catalyst in the isothermalreactor; and (iii) returning the first reactor effluent to theisothermal reactor after rejuvenating the second naphtha reformingcatalyst. In some embodiments, the reactor system for carrying out anaphtha reforming process as disclosed herein can comprise twoisothermal reactors (e.g., a first isothermal reactor and a secondisothermal reactor) connected in parallel, such that when either thesecond naphtha reforming catalyst of the first isothermal reactor or thesecond naphtha reforming catalyst of the second isothermal reactorbecomes spent, the second isothermal reactor or the first isothermalreactor, respectively, could continue the naphtha reforming process,thereby providing for a continuous naphtha reforming process.

In an embodiment, a method of carrying out a naphtha reforming processas disclosed herein can comprise operating a naphtha reforming reactorsystem comprising a plurality of reactors until a reactor is deemed tocontain a spent catalyst, where each of the plurality of reactorscontains a catalyst comprising a zeolite capable of converting at leasta portion of a hydrocarbon feed stream to aromatic hydrocarbons;isolating the reactor containing the spent catalyst from a remainingplurality of reactors; restoring the ability of the reactor containingthe spent catalyst to convert at least a portion of the hydrocarbon feedstream to aromatic hydrocarbons; preparing the reactor to resumeconversion of the hydrocarbon feed stream; returning the reactor to thehydrocarbon feed stream by connecting the reactor to the remainingplurality of reactors; and resuming operations of the naphtha reformingreactor system to convert at least the portion of the hydrocarbon feedstream to aromatic hydrocarbons.

In an embodiment, a method of carrying out a naphtha reforming processfor producing aromatic hydrocarbons as disclosed herein canadvantageously display improvements in one or more processcharacteristics when compared to conventional methods of carrying out anaphtha reforming process for producing aromatic hydrocarbons. Inconventional methods of carrying out a naphtha reforming process forproducing aromatic hydrocarbons, typically at least 5-10 adiabaticreactors operating in series are used for achieving a desired conversionof the convertible hydrocarbons to aromatic hydrocarbons. In anembodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can advantageously employ 1-2 adiabaticreactors and 1-2 isothermal reactors to achieve a similar desiredconversion of the convertible hydrocarbons to aromatic hydrocarbons,thereby reducing capital and operating costs. The adiabatic reactor(s)will suffer the biggest portion of the endotherm associated with thenaphtha reforming reactions by converting the easily convertiblehydrocarbons, thus reducing the heat flux at the upstream end of the ofthe plurality of tubes of the isothermal reactor, thus making itpossible to run the remainder of the naphtha reforming reactions in anisothermal reactor without the metallurgical problems or high alloysteels associated with operation at such high heat flux levels.

In an embodiment, the first reactor (e.g., adiabatic reactor) canadvantageously serve in an early warning capacity in case of feedcontamination with sulfur. In case of loss of endotherm in the firstreactor, the feed can be shut off and the naphtha reforming catalyst ofthe second reactor (e.g., downstream isothermal reactor) can beprotected from contamination with sulfur. The contamination warningcapability of the first reactor can advantageously eliminate the needfor a sulfur converter adsorber (SCA). A further advantage of removingthe SCA is that any aromatics in the feed would need to be converted tocycloalkanes in the SCA which would then be converted to aromatics onceagain in the naphtha reforming section of the plant. So, the ultimateconversion and the ultimate % aromatics content in the effluent wouldboth benefit by the presence of aromatics in the feed. With the SCA, thepresence of aromatics in the feed is detrimental to overall plantperformance.

As a further advantage of the reactor system and methods disclosedherein, the operating conditions of the naphtha reforming reactions canbe altered to produce further operational advantages. In an embodiment,the operating conditions of the naphtha reforming process may be reducedin severity using the systems and methods disclosed herein. For example,the pressures and temperatures used in the system, including a naphthareforming reactor section, may be reduced. In an embodiment, thetemperatures within the system may be maintained below about 1,000° F.(538° C.), alternatively below about 950° F. (510° C.), or alternativelybelow about 900° F. (482° C.), which could in turn decreasecarburization and metal loss rates. The reduction of the operatingtemperature may result in decreased conversion efficiency in theadiabatic reactor(s). In order to compensate for this reduction inconversion efficiency, a recycle stream comprising the unreactedreactants may be used to produce an overall equivalent conversionefficiency, or the reactors may be resized as needed. A plurality ofrecycle lines may be used within the system to allow for multiplerecycle configurations within the reactor system. Further, the reductionin operating temperature may allow for the reduction or elimination ofhigh temperature piping alloys and/or metal protective layers on thesurfaces of the piping and equipment contacting the hydrocarbon feedstream as described above. The reduction or elimination of hightemperature piping alloys and/or the metal protective layers mayrepresent a significant cost savings in the overall system. A decreasein the severity of the operating conditions can also result in anincreased catalyst life such that the catalyst deactivates at a slowerrate.

A decrease in the highest temperatures which would normally be seen inthe adiabatic configuration will results in a decrease in the amount ofunwanted cracking of hydrocarbons to light gases (e.g. methane).

In an embodiment, the naphtha reforming catalyst of the second reactor(e.g., isothermal reactor) can be advantageously active substantially atall times, as opposed to the naphtha reforming catalyst of the adiabaticreactors where only a portion of the reforming catalyst is above theendothermic reaction threshold temperature, and thus active. In theadiabatic reactor, the reforming catalyst that is below the endothermicreaction threshold temperature due to heat loss to the endothermicreaction is mostly inactive. At the start of the run, and for much ofthe run, this unused catalyst represents the majority of the catalyst inthe reactor. The catalyst being active all the time in the isothermalreactor can advantageously allow for using a smaller amount of catalyst.The use of a graded catalyst bed (both in activity and in particle size)can advantageously allow for operation and maintenance of isothermalnaphtha reforming conditions, where the necessary amount ofcatalytically active metal (e.g., group VIII metal, Pt) is reduced dueto the fact that substantially all of the catalytically active metal inthe isothermal reactor is employed at all times, as opposed to anadiabatic reactor where a large portion of the catalytically activemetal is idle at any given time. Further, the tubular design of theisothermal reactor can be more amenable to in situ catalyst rejuvenationwhen compared to a radial flow reactor. A feed system for halides couldbe added to allow for in situ rejuvenation of the catalyst in theisothermal reactor(s).

In an embodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can advantageously allow for recovering aportion of the heat of reactor effluents by using such effluent streamsin heat exchangers for heating hydrocarbon feed streams into thereactors, as previously described herein.

In an embodiment, a reactor system for carrying out a naphtha reformingprocess as disclosed herein can advantageously allow for continuousoperation by using reactors coupled in parallel, e.g., two or moreadiabatic reactors in parallel and two or more isothermal reactors inparallel. Restoring the catalyst activity in one reactor would notnecessitate an entire plant shutdown. Further, if increased productionwas desired (e.g., to accommodate higher feed rates), another isothermalreactor could be added in parallel with the existing isothermalreactor(s); and/or another adiabatic reactor could be added in parallelwith the existing adiabatic reactor(s).

In an embodiment, the use of a graded catalyst bed in the second reactor(e.g., isothermal reactor) can advantageously result in a decreasedpressure drop along the isothermal reactor. Further, eliminating SCAsfrom the reactor system can allow for a further decrease in overallpressure drop in the reactor system. A lower pressure drop can generallyresult in operating (e.g., compressor, and associated energy) savings.Lower cycle pressure drop allows for lower inlet pressures, and lowerpressures allow for increased conversion (the reaction has an increasein moles, so lower pressures aid in conversion). The graded catalyst bednot only gives lesser pressure drop, but the rate of pressure dropincrease over the run is lessened. In particular, the rate of plugging(or pressure drop increase) in the top zone of the isothermal reactor isreduced significantly. It is the first or top zone that is mostsusceptible to plugging and pressure drop increases. Additionaladvantages of the systems and/or methods of carrying out a naphthareforming process for producing aromatic hydrocarbons as disclosedherein can be apparent to one of skill in the art viewing thisdisclosure.

The present disclosure is further illustrated by the following examples,which are not to be construed in any way as imposing limitations uponthe scope thereof. On the contrary, it is to be clearly understood thatresort can be had to various other aspects, embodiments, modifications,and equivalents thereof which, after reading the description herein, canbe suggest to one of ordinary skill in the art without departing fromthe spirit of the present invention or the scope of the appended claims.

EXAMPLES

The disclosure having been generally described, the following examplesdemonstrate the practice and advantages thereof. It is understood thatthe examples are given by way of illustration and are not intended tolimit the specification of the claims to follow in any manner.

Example 1

The crush strength of naphtha reforming catalyst particles wasinvestigated in accordance with ASTM method D 6175-98 “Standard TestMethod for Radial Crush Strength of Extruded Catalyst,” with theexception that the force applied to the sample is applied laterally.⅛^(th) inch (3.2 mm) extrudates were used for testing. The force wasapplied at 3.80 lb/mm to catalyst particles with dimensions of 0.3783inches length and 0.1260 inches diameter, and the data are displayed inTable 1.

TABLE 1 Expected Target Sample Sample Sample Physical Analysis RangeValue #1 #2 #3 Crush Strength [lb] min 5.0 7.50 10.14 11.35 11.77 Crush[lb/mm] 2.44 2.65 2.61 Length [inches] 0.10-0.35 0.15 0.16 0.17 0.18Diameter [inches] 0.062-0.074 0.068 0.064 0.063 0.064

Additional Embodiments

The following are nonlimiting, specific embodiments in accordance withthe present disclosure:

Part A

A first embodiment, which is a method comprising introducing ahydrocarbon feed stream to a first reactor operating under adiabaticnaphtha reforming conditions, wherein the first reactor comprises afirst naphtha reforming catalyst and wherein the hydrocarbon feed streamcomprises a convertible hydrocarbon; converting at least a portion ofthe convertible hydrocarbon in the hydrocarbon feed stream to anaromatic hydrocarbon in the first reactor to form a first reactoreffluent; passing the first reactor effluent from the first reactor to asecond reactor operating under isothermal naphtha reforming conditions,wherein the second reactor comprises a second naphtha reforming catalystand wherein the first naphtha reforming catalyst and the second naphthareforming catalyst are the same or different; converting at least anadditional portion of the convertible hydrocarbon in the first reactoreffluent to an additional amount of the aromatic hydrocarbon in thesecond reactor to form a second reactor effluent; and recovering thesecond reactor effluent from the second reactor.

A second embodiment, which is the method of the first embodiment furthercomprising: heating the hydrocarbon feed stream in a first furnace priorto introducing the hydrocarbon feed stream to the first reactor.

A third embodiment, which is the method of any one of the first and thesecond embodiments, wherein the first reactor comprises a radial flowreactor.

A fourth embodiment, which is the method of any one of the first throughthe third embodiments, wherein the second reactor comprises a pluralityof tubes with particles of the second naphtha reforming catalystdisposed therein, wherein the plurality of tubes is disposed within areactor furnace.

A fifth embodiment, which is the method of the fourth embodiment,wherein the plurality of tubes is heated by burners in the reactorfurnace.

A sixth embodiment, which is the method of any one of the first throughthe fifth embodiments further comprising heating the first reactoreffluent within the reactor furnace, wherein heating the first reactoreffluent within the second reactor occurs during the converting.

A seventh embodiment, which is the method of any one of the firstthrough the sixth embodiments further comprising heating the firstreactor effluent in a second furnace prior to passing the first reactoreffluent into the second reactor.

An eighth embodiment, which is the method of the seventh embodiment,wherein heating the first reactor effluent comprises heating the firstreactor effluent while cooling the second reactor effluent by heatexchange in a feed effluent heat exchanger to produce a feed effluentheat exchanger effluent.

A ninth embodiment, which is the method of any one of the first throughthe eighth embodiments, wherein the second reactor is disposed within areactor furnace, wherein the reactor furnace comprises a radiant zoneand a convection zone, and wherein heating the first reactor effluentcomprises heating the first reactor effluent within tubes disposedwithin the convection zone.

A tenth embodiment, which is the method of any one of the first throughthe ninth embodiments further comprising processing the hydrocarbon feedstream with a bed of a sulfur adsorbing material within a preliminaryreactor prior to introducing the hydrocarbon feed stream to the firstreactor.

An eleventh embodiment, which is the method of the tenth embodiment,wherein the bed of the sulfur adsorbing material comprises potassiumhydroxide on alumina.

A twelfth embodiment, which is the method of any one of the firstthrough the eleventh embodiments, wherein the bed of the sulfuradsorbing material within the preliminary reactor is preceded by a bedof a sulfur converting material comprising Pt on alumina.

A thirteenth embodiment, which is the method of any one of the firstthrough the twelfth embodiments, wherein the preliminary reactorcontains the first naphtha reforming catalyst, the second naphthareforming catalyst, a third reforming catalyst, or combinations thereofas the sulfur adsorbing material.

A fourteenth embodiment, which is the method of any one of the firstthrough the thirteenth embodiments further comprising heating thehydrocarbon feed stream while cooling the second reactor effluent byheat exchange between the second reactor effluent with the hydrocarbonfeed stream.

A fifteenth embodiment, which is the method of any one of the firstthrough the fourteenth embodiments further comprising heating the firstreactor effluent while cooling the second reactor effluent by heatexchange between the second reactor effluent and the first reactoreffluent.

A sixteenth embodiment, which is the method of any one of the firstthrough the fifteenth embodiments, wherein the second naphtha reformingcatalyst, the first naphtha reforming catalyst, or both comprise azeolitic naphtha reforming catalyst.

A seventeenth embodiment, which is a reactor system comprising a firstreactor comprising a first inlet and a first outlet, wherein the firstreactor is configured to operate as an adiabatic reactor, and whereinthe first reactor comprises a first naphtha reforming catalyst; and asecond reactor comprising a second inlet and a second outlet, whereinthe second inlet is in fluid communication with the first outlet of thefirst reactor, wherein the second reactor is configured to operate as anisothermal reactor, wherein the second reactor comprises a secondnaphtha reforming catalyst, and wherein the first naphtha reformingcatalyst and the second naphtha reforming catalyst are the same ordifferent.

An eighteenth embodiment, which is the reactor system of the seventeenthembodiment, wherein the first reactor comprises a radial flow reactor.

A nineteenth embodiment, which is the reactor system of any one of theseventeenth and the eighteenth embodiments, wherein the second reactorcomprises a plurality of tubes disposed within a reactor furnace,wherein each tube of the plurality of tubes comprises the second naphthareforming catalyst.

A twentieth embodiment, which is the reactor system of the nineteenthembodiment, wherein the plurality of tubes does not contain a metalprotective layer comprising stannide.

A twenty-first embodiment, which is the reactor system of any one of theseventeenth through the twentieth embodiment, wherein the first inlet,the second inlet, or both are configured to be maintained at atemperature of less than 1000° F. (538° C.).

A twenty-second embodiment, which is the reactor system of any one ofthe seventeenth through the twenty-first embodiments further comprisingtubes disposed within a first furnace in fluid communication with thefirst inlet, wherein the first furnace is configured to heat ahydrocarbon feed stream prior to the hydrocarbon feed stream enteringthe first inlet.

A twenty-third embodiment, which is the reactor system of any one of theseventeenth through the twenty-second embodiments further comprisingtubes disposed within a second furnace in fluid communication with thesecond inlet, wherein the second furnace is configured to heat a firstreactor effluent stream prior to the first reactor effluent streamentering the second inlet.

A twenty-fourth embodiment, which is the reactor system of any one ofthe seventeenth through the twenty-third embodiments further comprisingheat exchange tubes disposed within a convection zone of the reactorfurnace in fluid communication with the second inlet, wherein thereactor furnace is configured to heat a first reactor effluent streamprior to the first reactor effluent stream entering the second inlet.

A twenty-fifth embodiment, which is the reactor system of thetwenty-second embodiment further comprising a preliminary reactor influid communication with the first inlet, wherein the preliminaryreactor is upstream of the first furnace.

A twenty-sixth embodiment, which is the reactor system of any one of theseventeenth through the twenty-fifth embodiments further comprising aheat exchanger, wherein the heat exchanger is configured to providethermal contact between a fluid passing through the second outlet and afluid passing through the first outlet.

A twenty-seventh embodiment, which is the reactor system of any one ofthe seventeenth through the twenty-sixth embodiments further comprisinga heat exchanger, wherein the heat exchanger is configured to providethermal contact between a fluid passing through the second outlet and afluid passing into the second inlet.

A twenty-eighth embodiment, which is the reactor system of any one ofthe seventeenth through the twenty-seventh embodiments furthercomprising a third reactor comprising a third inlet and a third outlet,wherein the third reactor is configured to operate as an adiabaticreactor, wherein the third reactor comprises a third reforming catalyst,and wherein the third outlet is in fluid communication with the firstinlet, wherein the third reforming catalysts is the same or different asthe first naphtha reforming catalyst or the second naphtha reformingcatalyst.

A twenty-ninth embodiment, which is the reactor system of any one of theseventeenth through the twenty-eighth embodiments, wherein the reactorsystem does not comprise a sulfur converter adsorber.

A thirtieth embodiment, which is a reactor system comprising a pluralityof adiabatic reactors, wherein each adiabatic reactor of the pluralityof adiabatic reactors comprises a first naphtha reforming catalyst; afeed header fluidly coupled to at least one of the plurality ofadiabatic reactors by one or more feed lines; an intermediate productheader fluidly coupled to at least one of the plurality of adiabaticreactors by one or more product lines; one or more isothermal reactorsfluidly coupled to the intermediate product header by one or more inletlines, wherein the one or more isothermal reactors comprise a secondnaphtha reforming catalyst and wherein the first naphtha reformingcatalyst and the second naphtha reforming catalyst are the same ordifferent; and an effluent header fluidly coupled to the one or moreisothermal reactors by one or more effluent lines, wherein a serial flowpath is formed from the feed header, through one or more of theplurality of adiabatic reactors, through the intermediate productheader, through at least one of the one or more isothermal reactors, andto the effluent header.

A thirty-first embodiment, which is the reactor system of the thirtiethembodiment further comprising a plurality of furnaces, wherein eachfurnace of the plurality of furnaces corresponds to one of the adiabaticreactors of the plurality of adiabatic reactors, wherein each furnace ofthe plurality of furnaces is fluidly coupled between a correspondingadiabatic reactor and the feed header.

A thirty-second embodiment, which is the reactor system of any one ofthe thirtieth and the thirty-first embodiments, wherein the plurality ofadiabatic reactors are arranged in series between the feed header andthe intermediate product header.

A thirty-third embodiment, which is the reactor system of any one of thethirtieth and the thirty-first embodiments, wherein the plurality ofadiabatic reactors are arranged in parallel between the feed header andthe intermediate product header.

A thirty-fourth embodiment, which is the reactor system of any one ofthe thirtieth through the thirty-third embodiments, wherein the one ormore isothermal reactors comprise two or more isothermal reactorsarranged in parallel between the intermediate product header and theeffluent header.

A thirty-fifth embodiment, which is the reactor system of any one of thethirtieth through the thirty-fourth embodiments, wherein the pluralityof adiabatic reactors comprises a plurality of radial flow reactors.

A thirty-sixth embodiment, which is the reactor system of any one of thethirtieth through the thirty-fifth embodiments further comprising acatalyst rejuvenation system coupled to the plurality of adiabaticreactors by a plurality of flow lines; and a plurality of valvesdisposed in the one or more feed lines, the one or more product lines,and the flow lines, wherein the plurality of valves are configured to bedynamically operated to isolate at least one of the adiabatic reactorsof the plurality of adiabatic reactors and fluidly couple the at leastone isolated adiabatic reactor to the catalyst rejuvenation system whilethe remaining adiabatic reactors remain operational.

A thirty-seventh embodiment, which is the reactor system of any one ofthe thirtieth through the thirty-sixth embodiments further comprising acatalyst rejuvenation system coupled to one or more isothermal reactorsby a plurality of flow lines; and a plurality of valves disposed in theone or more inlet lines, the one or more effluent lines, and the flowlines, wherein the plurality of valves are configured to be dynamicallyoperated to isolate at least one isothermal reactor of the one or moreisothermal reactors and fluidly couple the at least one isolatedisothermal reactor to the catalyst rejuvenation system while theremaining isothermal reactors remain operational.

A thirty-eighth embodiment, which is the reactor system of any one ofthe thirty-sixth and the thirty-seventh embodiments, wherein thecatalyst rejuvenation system comprises a halide source whereby halide isadded to the first naphtha reforming catalyst, the second naphthareforming catalyst, or both during rejuvenation.

Part B

A first embodiment, which is a method comprising introducing ahydrocarbon feed stream to a first reactor operating under adiabaticnaphtha reforming conditions, wherein the first reactor comprises afirst naphtha reforming catalyst, and wherein the hydrocarbon feedstream comprises a convertible hydrocarbon; converting at least aportion of the convertible hydrocarbon in the hydrocarbon feed stream toan aromatic hydrocarbon in the first reactor to form a first reactoreffluent; passing the first reactor effluent from the first reactor to asecond reactor operating under isothermal naphtha reforming conditions,wherein the second reactor comprises a second naphtha reformingcatalyst, and wherein the first naphtha reforming catalyst and thesecond naphtha reforming catalyst are the same or different; convertingat least an additional portion of the convertible hydrocarbon in thefirst reactor effluent to an additional amount of the aromatichydrocarbon in the second reactor to form a second reactor effluent; andrecovering the second reactor effluent from the second reactor, whereinan amount of the first naphtha reforming catalyst in the first reactoris less than an amount of the second naphtha reforming catalyst in thesecond reactor.

A second embodiment, which is the method of the first embodiment furthercomprising heating the hydrocarbon feed stream in a first furnace priorto introducing the hydrocarbon feed stream to the first reactor.

A third embodiment, which is the method of any one of the first and thesecond embodiments, wherein an operating temperature in the firstreactor does not exceed 1,000° F. (538° C.).

A fourth embodiment, which is the method of any one of the first throughthe third embodiments, wherein an operating temperature in the secondreactor does not exceed 1,000° F. (538° C.).

A fifth embodiment, which is the method of any one of the first throughthe fourth embodiments, wherein the second reactor comprises a pluralityof tubes with particles of the second naphtha reforming catalystdisposed therein, wherein the plurality of tubes is disposed within areactor furnace, and wherein the method further comprises: heating thefirst reactor effluent within the reactor furnace.

A sixth embodiment, which is the method of the fifth embodiment, theplurality of tubes is heated by burners in the reactor furnace.

A seventh embodiment, which is the method of any one of the firstthrough the fifth embodiments, wherein the plurality of tubes is heatedby a heat exchange medium or a molten salt.

An eighth embodiment, which is the method of any one of the firstthrough the seventh embodiments, wherein at least one tube of theplurality of tubes contains a plurality of catalyst zones.

A ninth embodiment, which is the method of the eighth embodiment,wherein the first reactor effluent contacts a mixture of catalystparticles and a first material in a first catalyst zone of the pluralityof catalyst zones to produce a first catalyst zone effluent, wherein thefirst catalyst zone is the first catalyst zone of the plurality ofcatalyst zones contacted by the first reactor effluent.

A tenth embodiment, which is the method of the ninth embodiment, whereinthe first material comprises an inert material, a less active naphthareforming catalyst material, or a mixture of both.

An eleventh embodiment, which is the method of any one of the firstthrough the tenth embodiments, wherein the first catalyst zone effluentcontacts a second catalyst zone of the plurality of catalyst zones toproduce a second catalyst zone effluent, wherein the second catalystzone contains a second mixture of catalyst particles and a secondmaterial, wherein the weight ratio of the amount of catalyst particlesto the second material is higher in the second catalyst zone than theweight ratio of the amount of the catalyst particles to the firstmaterial in the first catalyst zone, wherein the first catalyst zone isupstream of the second catalyst zone, and wherein the weight ratio isbased on the weight of the catalyst when loaded.

A twelfth embodiment, which is the method of the eleventh embodiment,wherein the second material comprises an inert material, a less activenaphtha reforming catalyst material, or a mixture of both.

A thirteenth embodiment, which is the method of any one of the firstthrough the eighth embodiments, wherein the first reactor effluentcontacts catalyst particles in a first catalyst zone of the plurality ofcatalyst zones to produce a first catalyst zone effluent, wherein thefirst catalyst zone is the first catalyst zone of the plurality ofcatalyst zones contacted by the first reactor effluent; wherein thefirst catalyst zone effluent contacts a second catalyst zone of theplurality of catalyst zones to produce a second catalyst zone effluent,wherein the second catalyst zone contains a second zone mixture ofcatalyst particles and a second material, wherein the first catalystzone is upstream of the second catalyst zone; and wherein the secondcatalyst zone effluent contacts a third catalyst zone of the pluralityof catalyst zones to produce a third catalyst zone effluent, wherein thethird catalyst zone contains catalyst particles or a third zone mixtureof catalyst particles and a third material, wherein the third catalystzone is downstream of the second catalyst zone, and wherein the thirdcatalyst zone is the last catalyst zone of the plurality of catalystzones contacted by the first reactor effluent.

A fourteenth embodiment, which is the method of the thirteenthembodiment, wherein the third zone mixture comprises an inert material,an isomerization catalyst, or a mixture of both an inert material and anisomerization catalyst.

A fifteenth embodiment, which is the method of any one of the firstthrough the eighth embodiments, wherein the first reactor effluentcontacts a first catalyst zone of the plurality of catalyst zones toproduce a first catalyst zone effluent, wherein the first catalyst zonecontains a first zone mixture of catalyst particles and a firstmaterial, wherein the first catalyst zone is the first catalyst zone ofthe plurality of catalyst zones contacted by the first reactor effluent;wherein the first catalyst zone effluent contacts a second catalyst zoneof the plurality of catalyst zones to produce a second catalyst zoneeffluent, wherein the second catalyst zone contains catalyst particles,wherein the first catalyst zone is upstream of the second catalyst zone;and wherein the second catalyst zone effluent contacts a third catalystzone of the plurality of catalyst zones to produce a third catalyst zoneeffluent, wherein the third catalyst zone contains catalyst particles ora third zone mixture of catalyst particles and a third material, whereinthe third catalyst zone is downstream of the second catalyst zone, andwherein the third catalyst zone is the last catalyst zone of theplurality of catalyst zones contacted by the first reactor effluent.

A sixteenth embodiment, which is the method of the fifteenth embodiment,wherein the third zone mixture comprises an inert material, anisomerization catalyst, or a mixture of both an inert material and anisomerization catalyst.

A seventeenth embodiment, which is the method of any one of the firstthrough the twelfth embodiments, wherein the second catalyst zoneeffluent contacts the remaining catalyst zones of the plurality ofcatalyst zones, wherein each catalyst zone of the plurality of catalystzones comprises an increasing amount of catalyst particles from anupstream to a downstream direction, and wherein a final catalyst zone ofthe plurality of catalysts zones contains none of the first material ornone of the second material, wherein the final catalyst zone is the mostdownstream catalyst zone of the plurality of catalyst zones.

An eighteenth embodiment, which is the method of any one of the firstthrough the seventeenth embodiments, wherein a first catalyst zone ofthe plurality of catalyst zones comprises a first catalyst materialhaving a first particle size, wherein a second catalyst zone of theplurality of catalyst zones comprises a second catalyst material havinga second particle size, wherein the first particle size is larger thanthe second particle size, and wherein the first catalyst zone isupstream of the second catalyst zone.

A nineteenth embodiment, which is the method of any one of the firstthrough the eighteenth embodiments further comprising passing thehydrocarbon feed stream through a preliminary reactor to form apreliminary reactor effluent.

A twentieth embodiment, which is the method of the nineteenthembodiment, wherein the preliminary reactor contains a sulfur controlsorbent alone or in combination with a sulfur converting material, andwherein the method further comprises removing a portion of the sulfur inthe hydrocarbon feed stream with the preliminary reactor; and detectinga first sulfur level in the hydrocarbon feed stream upstream of thepreliminary reactor; detecting a second sulfur level in the hydrocarbonfeed stream downstream of the preliminary reactor; and ceasing theintroduction of the feed stream to the first reactor when a reduction inthe sulfur level between the first sulfur level and the second sulfurlevel is less than a threshold.

A twenty-first embodiment, which is the method of any one of the firstthrough the twentieth embodiments, wherein the preliminary reactorcontains a third reforming catalyst and wherein the first naphthareforming catalyst; the second naphtha reforming catalyst and the thirdreforming catalyst are the same or different, and wherein the methodfurther comprises detecting a decrease in temperature between thehydrocarbon feed stream and the preliminary reactor effluent; andceasing the introduction of the hydrocarbon feed stream to thepreliminary reactor when the decrease in the temperature is less than athreshold.

A twenty-second embodiment, which is the method of the twenty-firstembodiment, wherein the decrease in temperature of less than thethreshold is due to deactivation of at least a portion of the thirdreforming catalyst due to the presence of sulfur in the hydrocarbon feedstream.

A twenty-third embodiment, which is the method of any one of the firstthrough the twenty-second embodiments further comprising ceasing passingthe first reactor effluent to the second reactor operating underisothermal reactor conditions; rejuvenating the second naphtha reformingcatalyst in the second reactor; and returning the first reactor effluentto the second reactor after rejuvenating the second naphtha reformingcatalyst.

A twenty-fourth embodiment, which is the method of any one of the firstthrough the twenty-third embodiments, wherein the first reactorcomprises a radial flow reactor.

A twenty-fifth embodiment, which is a naphtha reforming reactor systemcomprising a first reactor comprising a first inlet and a first outlet,wherein the first reactor is configured to operate as an adiabaticreactor, and wherein the first reactor comprises a first naphthareforming catalyst; and a second reactor comprising a second inlet and asecond outlet, wherein the second inlet is in fluid communication withthe first outlet of the first reactor, wherein the second reactor isconfigured to operate as an isothermal reactor, and wherein the secondreactor comprises a plurality of tubes disposed within a reactorfurnace, a heat source configured to heat the interior of the reactorfurnace; and a second naphtha reforming catalyst disposed within theplurality of tubes, wherein the first naphtha reforming catalyst and thesecond naphtha reforming catalyst are the same or different.

A twenty-sixth embodiment, which is the reactor system of thetwenty-fifth embodiment, wherein the plurality of tubes comprisesbetween about 250 to about 5,000 tubes in the furnace.

A twenty-seventh embodiment, which is the reactor system of any one ofthe twenty-fifth and the twenty-sixth embodiments, wherein the pluralityof tubes have a length to diameter ratio between about 25 and about 150.

A twenty-eighth embodiment, which is the reactor system of any one ofthe twenty-fifth through the twenty-seventh embodiments, wherein theplurality of tubes have an internal diameter between about 0.5 inches(13 mm) and about 4.0 inches (102 mm).

A twenty-ninth embodiment, which is the reactor system of any one of thetwenty-fifth through the twenty-eighth embodiments, wherein at least onetube of the plurality of tubes has a plurality of catalyst zones.

A thirtieth embodiment, which is the reactor system of the twenty-ninthembodiment, wherein a first catalyst zone of the plurality of catalystzones comprises a mixture of a naphtha reforming catalyst particles andan inert material, a less active naphtha reforming catalyst material, ora mixture of both and wherein the first catalyst zone is disposed on anupstream end of the at least one tube within the reactor furnace.

A thirty-first embodiment, which is the reactor system of any one of thetwenty-fifth through the thirtieth embodiments, wherein a secondcatalyst zone of the plurality of catalyst zones comprises only anaphtha reforming catalyst without the inert material, and wherein thesecond catalyst zone is disposed downstream of the first catalyst zone.

A thirty-second embodiment, which is the reactor system of any one ofthe twenty-fifth and the thirty-first embodiments, wherein each catalystzone of the plurality of catalyst zones comprises an increasing amountof the naphtha reforming catalyst particles and a decreasing amount ofless active naphtha reforming catalyst material from an upstream to adownstream direction, and wherein a final catalyst zone of the pluralityof catalysts zones contains no less active naphtha reforming catalystmaterial, wherein the final catalyst zone is the most downstreamcatalyst zone of the plurality of catalyst zones.

A thirty-third embodiment, which is the reactor system of thethirty-second embodiment, wherein the final catalyst zone of theplurality of catalysts zones comprises a mixture of a naphtha reformingcatalyst and an isomerization catalyst, wherein the final catalyst zoneis the most downstream catalyst zone of the plurality of catalyst zones.

A thirty-fourth embodiment, which is the reactor system of any one ofthe twenty-fifth through the thirty-third embodiments, wherein a firstcatalyst zone of the plurality of catalyst zones comprises a firstcatalyst material having a first particle size, wherein a secondcatalyst zone of the plurality of catalyst zones comprises a secondcatalyst material having a second particle size, wherein the firstparticle size is larger than the second particle size, and wherein thefirst catalyst zone is located upstream of the second catalyst zone inthe at least one tube.

A thirty-fifth embodiment, which is the reactor system of any one of thetwenty-fifth through the thirty-fourth embodiments, wherein at least onetube of the plurality of tubes comprises a graded catalyst bed.

A thirty-sixth embodiment, which is the reactor system of thethirty-fifth embodiment, wherein the graded catalyst bed comprises anincreasing amount of the second naphtha reforming catalyst disposed inthe at least one tube per unit volume along a length of the at least onetube in a flow direction and wherein the balance of the material perunit volume is an inert material, a less active naphtha reformingcatalyst material, or a mixture of both.

A thirty-seventh embodiment, which is the reactor system of any one ofthe twenty-fifth through the thirty-sixth embodiments, wherein the firstreactor comprises a radial flow reactor.

A thirty-eighth embodiment, which is the reactor system of any one ofthe twenty-fifth through the thirty-seventh embodiments, wherein a ratioof an amount of the first naphtha reforming catalyst in the firstreactor to an amount of the second naphtha reforming catalyst in thesecond reactor is in the range of about 1:2 to about 1:10 by weight offresh catalyst.

A thirty-ninth embodiment, which is the reactor system of any one of thetwenty-fifth through the thirty-eighth embodiments, wherein theplurality of tubes does not contain a metal protective layer comprisingstannide.

A fortieth embodiment, which is the reactor system of any one of thetwenty-fifth through the thirty-ninth embodiments, wherein an amount ofthe second naphtha reforming catalyst is configured to be substantiallyfully utilized when the second naphtha reforming catalyst disposedwithin the plurality of tubes is operating above an endothermic reactionthreshold temperature.

A forty-first embodiment, which is a method comprising introducing ahydrocarbon feed stream to a radial flow reactor operating underadiabatic naphtha reforming conditions, wherein the radial flow reactorcomprises a first naphtha reforming catalyst, and wherein thehydrocarbon feed stream comprises a convertible hydrocarbon; convertingat least a portion of the convertible hydrocarbon in the hydrocarbonfeed stream to an aromatic hydrocarbon in the radial flow reactor toform a first reactor effluent; passing the first reactor effluent fromthe radial flow reactor to a second reactor operating under isothermalnaphtha reforming conditions, wherein the second reactor comprises aplurality of tubes disposed within a reactor furnace, and a secondnaphtha reforming catalyst disposed within the plurality of tubes, andwherein the plurality of tubes are arranged in parallel between an inletand an outlet of the reactor furnace; passing the first reactor effluentthrough the plurality of tubes within the second reactor; converting atleast an additional portion of the convertible hydrocarbon in the firstreactor effluent to an addition amount of the aromatic hydrocarbon inthe second reactor to form a second reactor effluent, wherein theplurality of tubes is heated within the reactor furnace during theconverting; and recovering the second reactor effluent from the secondreactor.

A forty-second embodiment, which is the method of the forty-firstembodiment, wherein an operating temperature in the radial flow reactordoes not exceed 1,000° F. (538° C.), and wherein an operatingtemperature in the second reactor does not exceed 1,000° F. (538° C.).

A forty-third embodiment, which is the method of any one of theforty-first and the forty-second embodiments, wherein the first reactoreffluent passes through a plurality of catalyst zones within at leastone tube of the plurality of tubes while being heated within the reactorfurnace.

A forty-fourth embodiment, which is the method of the forty-thirdembodiment, wherein the first reactor effluent contacts a mixture ofcatalyst particles and a first material in a first catalyst zone of theplurality of catalyst zones, wherein the first catalyst zone is thefirst catalyst zone of the plurality of catalyst zones contacted by thefirst reactor effluent, wherein the first reactor effluent then contactsa second mixture of catalyst particles and the first material in asecond catalyst zone of the plurality of catalyst zones, and wherein aratio of the volume of catalyst particles to the volume of the firstmaterial higher in the second catalyst zone than in the first catalystzone.

A forty-fifth embodiment, which is the method of any one of theforty-first through the forty-fourth embodiments, wherein a finalcatalyst zone of the plurality of catalysts zones contains none of thefirst material, wherein the final catalyst zone is the most downstreamcatalyst zone of the plurality of catalyst zones.

A forty-sixth embodiment, which is the method of any one of theforty-first through the forty-fifth embodiments, wherein the firstmaterial comprises an inert material, a less active naphtha reformingcatalyst material, or a mixture thereof.

A forty-seventh embodiment, which is the method of any one of theforty-first through the forty-sixth embodiments, wherein a firstcatalyst zone of the plurality of catalyst zones comprises a firstcatalyst material having a first particle size, wherein a secondcatalyst zone of the plurality of catalyst zones comprises a secondcatalyst material having a second particle size, wherein the firstparticle size is larger than the second particle size, and wherein thefirst catalyst zone is upstream of the second catalyst zone.

A forty-eighth embodiment, which is the method of any one of theforty-first through the forty-seventh embodiments, wherein the catalysthas a crush strength of greater than 4 pounds force (lbf, 17.8 N), asdetermined in accordance with ASTM method D 6175-98.

A forty-ninth embodiment, which is the method of any one of theforty-first through the forty-eighth embodiments, wherein a pressuredrop measured between an inlet of the plurality of tubes and an outletof the plurality of tubes is from about 1 psia (0.007 MPa) to about 20psia (0.1 MPa).

A fiftieth embodiment, which is the method of any one of the forty-firstthrough the forty-ninth embodiments, wherein the pressure at an inlet ofthe plurality of tubes is less than about 100 psig (0.69 MPa).

A fifty-first embodiment, which is the method of any one of theforty-first through the fiftieth embodiments, wherein a final catalystzone of the plurality of catalysts zones contains no first material,wherein the final catalyst zone comprises a mixture of catalystparticles and an isomerization catalyst, wherein the final catalyst zoneis the most downstream catalyst zone of the plurality of catalyst zones.

While the present disclosure has been illustrated and described in termsof particular apparatus and methods of use, it is apparent thatequivalent techniques, components, and constituents may be substitutedfor those shown, and other changes can be made within the scope of thepresent disclosure as defined by the appended claims.

The particular embodiments disclosed herein are illustrative only, asthe disclosure may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of the disclosure.Accordingly, the protection sought herein is as set forth in the claimsbelow.

We claim:
 1. A method comprising: introducing a hydrocarbon feed streamto a first reactor operating under adiabatic naphtha reformingconditions, wherein the first reactor comprises a first naphthareforming catalyst, and wherein the hydrocarbon feed stream comprises aconvertible hydrocarbon; converting at least a portion of theconvertible hydrocarbon in the hydrocarbon feed stream to an aromatichydrocarbon in the first reactor to form a first reactor effluent;passing the first reactor effluent from the first reactor to a secondreactor operating under isothermal naphtha reforming conditions, whereinthe second reactor comprises a second naphtha reforming catalyst, andwherein the first naphtha reforming catalyst and the second naphthareforming catalyst are the same or different; converting at least anadditional portion of the convertible hydrocarbon in the first reactoreffluent to an additional amount of the aromatic hydrocarbon in thesecond reactor to form a second reactor effluent; and recovering thesecond reactor effluent from the second reactor, wherein an amount ofthe first naphtha reforming catalyst in the first reactor is less thanan amount of the second naphtha reforming catalyst in the secondreactor.
 2. The method of claim 1, wherein the second reactor comprisesa plurality of tubes with particles of the second naphtha reformingcatalyst disposed therein, wherein the plurality of tubes is disposedwithin a reactor furnace, and wherein the method further comprises:heating the first reactor effluent within the reactor furnace.
 3. Themethod of claim 2, wherein at least one tube of the plurality of tubescontains a plurality of catalyst zones.
 4. The method of claim 3,wherein the first reactor effluent contacts a mixture of catalystparticles and a first material in a first catalyst zone of the pluralityof catalyst zones to produce a first catalyst zone effluent, wherein thefirst catalyst zone is the first catalyst zone of the plurality ofcatalyst zones contacted by the first reactor effluent; wherein thefirst material comprises an inert material, a less active naphthareforming catalyst material, or a mixture of both; wherein the firstcatalyst zone effluent contacts a second catalyst zone of the pluralityof catalyst zones to produce a second catalyst zone effluent, whereinthe second catalyst zone contains a second mixture of catalyst particlesand a second material, wherein the weight ratio of the amount ofcatalyst particles to the second material is higher in the secondcatalyst zone than the weight ratio of the amount of the catalystparticles to the first material in the first catalyst zone, wherein thefirst catalyst zone is upstream of the second catalyst zone, and whereinthe weight ratio is based on the weight of the catalyst when loaded; andwherein the second material comprises an inert material, a less activenaphtha reforming catalyst material, or a mixture of both.
 5. The methodof claim 4, wherein the second catalyst zone effluent contacts theremaining catalyst zones of the plurality of catalyst zones, whereineach catalyst zone of the plurality of catalyst zones comprises anincreasing amount of catalyst particles from an upstream to a downstreamdirection, and wherein a final catalyst zone of the plurality ofcatalysts zones contains none of the first material or none of thesecond material, wherein the final catalyst zone is the most downstreamcatalyst zone of the plurality of catalyst zones.
 6. The method of claim3, wherein a first catalyst zone of the plurality of catalyst zonescomprises a first catalyst material having a first particle size,wherein a second catalyst zone of the plurality of catalyst zonescomprises a second catalyst material having a second particle size,wherein the first particle size is larger than the second particle size,and wherein the first catalyst zone is upstream of the second catalystzone.
 7. A naphtha reforming reactor system comprising: a first reactorcomprising a first inlet and a first outlet, wherein the first reactoris configured to operate as an adiabatic reactor, and wherein the firstreactor comprises a first naphtha reforming catalyst; and a secondreactor comprising a second inlet and a second outlet, wherein thesecond inlet is in fluid communication with the first outlet of thefirst reactor, wherein the second reactor is configured to operate as anisothermal reactor, and wherein the second reactor comprises: aplurality of tubes disposed within a reactor furnace, a heat sourceconfigured to heat the interior of the reactor furnace; and a secondnaphtha reforming catalyst disposed within the plurality of tubes,wherein the first naphtha reforming catalyst and the second naphthareforming catalyst are the same or different, wherein at least one tubeof the plurality of tubes has a plurality of catalyst zones.
 8. Thenaphtha reforming reactor system of claim 7, wherein the plurality oftubes comprises between about 250 to about 5,000 tubes in the furnace.9. The naphtha reforming reactor system of claim 7, wherein theplurality of tubes have a length to diameter ratio between about 25 andabout 150; and wherein the plurality of tubes have an internal diameterbetween about 0.5 inches (13 mm) and about 4.0 inches (102 mm).
 10. Thenaphtha reforming reactor system of claim 7, wherein a first catalystzone of the plurality of catalyst zones comprises a mixture of a naphthareforming catalyst particles and an inert material, a less activenaphtha reforming catalyst material, or a mixture of both and whereinthe first catalyst zone is disposed on an upstream end of the at leastone tube within the reactor furnace.
 11. The naphtha reforming reactorsystem of claim 10, wherein a second catalyst zone of the plurality ofcatalyst zones comprises only a naphtha reforming catalyst without theinert material, and wherein the second catalyst zone is disposeddownstream of the first catalyst zone.
 12. The naphtha reforming reactorsystem of claim 10, wherein each catalyst zone of the plurality ofcatalyst zones comprises an increasing amount of the naphtha reformingcatalyst particles and a decreasing amount of less active naphthareforming catalyst material from an upstream to a downstream direction,and wherein a final catalyst zone of the plurality of catalysts zonescontains no less active naphtha reforming catalyst material, wherein thefinal catalyst zone is the most downstream catalyst zone of theplurality of catalyst zones.
 13. The naphtha reforming reactor system ofclaim 12, wherein the final catalyst zone of the plurality of catalystszones comprises a mixture of a naphtha reforming catalyst and anisomerization catalyst, wherein the final catalyst zone is the mostdownstream catalyst zone of the plurality of catalyst zones.
 14. Thenaphtha reforming reactor system of claim 7, wherein a first catalystzone of the plurality of catalyst zones comprises a first catalystmaterial having a first particle size, wherein a second catalyst zone ofthe plurality of catalyst zones comprises a second catalyst materialhaving a second particle size, wherein the first particle size is largerthan the second particle size, and wherein the first catalyst zone islocated upstream of the second catalyst zone in the at least one tube.15. A naphtha reforming reactor system comprising: a first reactorcomprising a first inlet and a first outlet, wherein the first reactoris configured to operate as an adiabatic reactor, and wherein the firstreactor comprises a first naphtha reforming catalyst; and a secondreactor comprising a second inlet and a second outlet, wherein thesecond inlet is in fluid communication with the first outlet of thefirst reactor, wherein the second reactor is configured to operate as anisothermal reactor, and wherein the second reactor comprises: aplurality of tubes disposed within a reactor furnace, a heat sourceconfigured to heat the interior of the reactor furnace; and a secondnaphtha reforming catalyst disposed within the plurality of tubes,wherein the first naphtha reforming catalyst and the second naphthareforming catalyst are the same or different, wherein at least one tubeof the plurality of tubes comprises a graded catalyst bed; and whereinthe graded catalyst bed comprises an increasing amount of the secondnaphtha reforming catalyst disposed in the at least one tube per unitvolume along a length of the at least one tube in a flow direction andwherein the balance of the material per unit volume is an insertmaterial, a less active naphtha reforming catalyst material, or mixtureof both.
 16. A naphtha reforming reactor system comprising: a firstreactor comprising a first inlet and a first outlet, and wherein thefirst reactor is configured to operate as an adiabatic reactor, andwherein the first reactor comprises a first naphtha reforming catalyst;and a second reactor comprising a second inlet and a second outlet,wherein the second inlet is in fluid communication with the first outletof the first reactor, wherein the second reactor is configured tooperate as an isothermal reactor, and wherein the second reactorcomprises: a plurality of tubes disposed within a reactor furnace, aheat source configure to heat the interior of the reactor furnace; and asecond naphtha reforming catalyst disposed within the plurality oftubes, wherein the first naphtha reforming catalyst and the secondnaphtha reforming catalyst are the same or different, and wherein aratio of an amount of the first naphtha reforming catalyst in the firstreactor to an amount of the second naphtha reforming catalyst in thesecond reactor is in the range of about 1:2 to about 1:10 by weight offresh catalyst.
 17. A naphtha reforming reactor system comprising: afirst reactor comprising a first inlet and a first outlet, wherein thefirst reactor is configured to operate as an adiabatic reactor, andwherein the first reactor comprises a first naphtha reforming catalyst;and a second reactor comprising a second inlet and a second outlet,wherein the second inlet is in fluid communication with the first outletof the first reactor, wherein the second reactor is configured tooperate as an isothermal reactor, and wherein the second reactorcomprises: a plurality of tubes disposed within a reactor furnace, aheat source configured to heat the interior of the reactor furnace; anda second naphtha reforming catalyst disposed within the plurality oftubes, wherein the first naphtha reforming catalyst and the secondnaphtha reforming catalyst are the same or different, and wherein anamount of the second naphtha reforming catalyst is configured to besubstantially fully utilized when the second naphtha reforming catalystdisposed within the plurality of tubes is operating above an endothermicreaction threshold temperature.
 18. A method comprising: introducing ahydrocarbon feed stream to a radial flow reactor operating underadiabatic naphtha reforming conditions, wherein the radial flow reactorcomprises a first naphtha reforming catalyst, and wherein thehydrocarbon feed stream comprises a convertible hydrocarbon; convertingat least a portion of the convertible hydrocarbon in the hydrocarbonfeed stream to an aromatic hydrocarbon in the radial flow reactor toform a first reactor effluent; passing the first reactor effluent fromthe radial flow reactor to a second reactor operating under isothermalnaphtha reforming conditions, wherein the second reactor comprises aplurality of tubes disposed within a reactor furnace, and a secondnaphtha reforming catalyst disposed within the plurality of tubes, andwherein the plurality of tubes are arranged in parallel between an inletand an outlet of the reactor furnace; passing the first reactor effluentthrough the plurality of tubes within the second reactor; converting atleast an additional portion of the convertible hydrocarbon in the firstreactor effluent to an addition amount of the aromatic hydrocarbon inthe second reactor to form a second reactor effluent, wherein theplurality of tubes is heated within the reactor furnace during theconverting; and recovering the second reactor effluent form the secondreactor.
 19. The method of claim 18, wherein the first reactor effluentpasses through a plurality of catalyst zones within at least one tube ofthe plurality of tubes while being heated within the reactor furnace.20. The method of claim 19, wherein the first reactor effluent contactsa mixture of catalyst particles and a first material in a first catalystzone of the plurality of catalyst zones, wherein the first catalyst zoneis the first catalyst zone of the plurality of catalyst zones contactedby the first reactor effluent, wherein the first reactor effluent thencontacts a second mixture of catalyst particles and the first materialin a second catalyst zone of the plurality of catalyst zones, andwherein a ratio of the volume of catalyst particles to the volume of thefirst material higher in the second catalyst zone than in the firstcatalyst zone; and wherein a final catalyst zone of the plurality ofcatalysts zones contains none of the first material, wherein the finalcatalyst zone is the most downstream catalyst zone of the plurality ofcatalyst zones.
 21. The method of claim 18, wherein the catalyst has acrush strength of greater than 4 pounds force (lbf, 17.8 N), asdetermined in accordance with ASTM method D 6175-98.
 22. The method ofclaim 18, wherein a pressure drop measured between an inlet of theplurality of tubes and an outlet of the plurality of tubes is from about1 psia (0.007 MPa) to about 20 psia (0.1 MPa).
 23. The method of claim18, wherein the pressure at an inlet of the plurality of tubes is lessthan about 100 psig (0.69 MPa).